If Marian Keyes ever needed to look for an alternative career to writing, there are several options she could definitely pursue. She could be a full-time tweeter, with 'Love/Hate', make-up and chocolate as her specialist subjects. She could bake cakes for a living, or she could give Laurence Llewelyn-Bowen a run for his money on the home-decorating front.
From the moment you set foot in her aquamarine-coloured house in south Co Dublin, you know that this is no ordinary dwelling. But, then again, it wouldn't be, given that it houses one of the most successful authors we've ever produced. More than 23 million copies of her 15 books have sold worldwide.
And curled up on the sofa in the stunning living room decorated in accents of pink, green and gold, Marian (49) is talking about her new-found love for Nidge, the star of the acclaimed RTE series, 'Love/Hate'.
Does she and her husband Tony have a 'list', and if so, who would be on hers?
"Oh God, yes," she laughs, "Definitely Nidge. My list is quite long now since most of 'Games of Thrones' are on it, plus 'Strictly Come Dancing' star Pasha Kovalev and 'Got To Dance' judge Ashley Banjo."
Television and box sets are twin passions for Marian, who says they helped her to come through the past three-and-a half years. During this time, she was gripped by a terrifying darkness, which she describes as a breakdown.
In October 2009, the author realised that the sands beneath her feet were shifting. The people and places she loved began to feel unfamiliar – even frightening – to her.
Her sleeping, eating, breathing and thinking patterns became dramatically disturbed, to the extent that when she and Tony went on holiday to Thailand, she was unable to handle it.
"The blue sea and sky appalled me, and the rocky landscape seemed so sinister that I couldn't look at it," she explains. "We had to come home early."
Marian was diagnosed with depression and given medication, but she continued to unravel. Her psychiatrist suggested admission to a psychiatric hospital in December 2009. In the few weeks she was there, the staff tried hard to help her to feel less afraid.
She begged to be allowed home, but found that she was unable to function, let alone write, and tried everything she could think of to bring a chink of light to the darkness.
"When you're desperate, you'd do anything," she says, "so I tried yoga, cognitive behavioural therapy, swimming, hill walking, meditation, Reiki, acupuncture, vitamin B12 injections, mindfulness, prayer, gratitude lists, random acts of kindness, staying in bed, zinc, and attending Padre Pio masses.
"None of the feckin' things worked. I felt incredibly worthless, because it's really difficult to go to bed at night and promise yourself that you will get up tomorrow and be useful and function like another member of society.
"And then morning comes and you find that you can't."
The only thing that helped her on one level was baking cakes. Indeed she released a recipe book called 'Saved by Cake' last year, with the Irish royalties going to St Vincent de Paul.
"I baked obsessively, and it was a great help, although I'd never been that type before," she says. "I kind of despised all that homey stuff, but I found myself sitting at the kitchen table, drawing faces on cupcakes and fiddling around with silver balls and hundreds and thousands – very childlike stuff. It didn't cure me, but it managed to colonise some of my brain, so it wasn't completely full of horror."
Marian says that her demeanour oscillated from mute, bed-bound catatonia to bouts of tearful grief or spells of manic anxiety.
Her beloved writing – always a therapeutic outlet – had come to a halt, despite all of the promises she kept making to herself of starting a new novel.
Eventually, after a year of agony, she slowly began to write 'The Mystery of Mercy Close'. It is the fifth of her books about the Walsh family, each one focusing on a different sister.
In 'Watermelon', we had Claire, whose husband leaves her. In 'Angels', Maggie is looking for more excitement than her stale marriage, and then there's Rachel, who enters rehab for alcohol addiction in 'Rachel's Holiday'. In 'Anyone Out There?', Anna is recovering from a terrible car crash.
'The Mystery of Mercy Close' is centred on Helen, the abrasive, courageous and difficult fifth sister, who works as a private investigator. It is released in paperback this weekend.
"When I started to write it, I was so catatonic and unable to think that I didn't think I would ever finish it," says Marian.
"I had no routine and it was very stop-starty. There were long spells of no work. But, eventually, the words mounted up, and when it came out in hardback, there was a lovely reaction to it and I was delighted.
"I'd always thought that I couldn't write a book about Helen, because she's just so horrible in ways and lacking in emotional intelligence. And usually my characters undergo an emotional deconstruction and reconstruction, but she's really tough and I didn't want her not to be tough."
In the book, Helen's dodgy ex-boyfriend and music manager Jay Parker asks her to find the missing Wayne Diffney, lead singer of the boyband Laddz. He has gone awol ahead of a lucrative comeback concert. As Helen tries to find him, she has romantic troubles with both Jay and her stable and sexy detective boyfriend, Artie Devlin. She also struggles with depression.
Exploring that aspect of her was therapeutic, reveals Marian.
"Her depression is very obviously mine, so that was nice to write about really," she says. "It meant that I could be honest, because I had spent a lot of time trying to mind the people around me and pretending that I wasn't as bad as I was. So when I was describing the way Helen's reality was altered by the chemicals in her head, it was nice to be able to be completely honest."
Her fictional heroine makes plans to commit suicide on two occasions, and Marian has drawn on the despair that she was feeling herself to write these difficult scenes.
Like Helen, Marian also bought a Stanley knife from a hardware shop in January 2010, and planned to take her own life.
Thankfully, she managed to get through the danger with the help of her therapist, and says that while those dark parts of the book were difficult to write, they were important.
"The thing is that I was extremely suicidal for a year and a half, and I had to fight it every day," she says.
"It's really heavy, and obviously I had other people and their feelings to think about, but they knew. I remember sobbing in my mother Mary's arms and begging her to give me permission to kill myself. We have an epidemic of suicide in this country and it's not talked about enough, so while it was hard to write about, it had to be done.
"The depression has been worse than anything else I've been through, including alcoholism and recovering from that, and I would happily have never written again just to get rid of it."
Marian says that there was a certain defiance to having the strong, sexy Helen Walsh battle depression, because it drives her mad when people think that it's something that can be fixed by going for a brisk walk or changing your attitude.
As she has written about themes that have touched her own life, the author says that she feels fortunate that her experiences can be channelled into a book that might touch someone else in their own pain.
"You see, I love reading things that I identify with," she explains.
"The only way you can feel that you're not alone is by hearing other people's stories. There are so many people who have gone through the darkness that I go through, but I feel uniquely lucky that my experiences can be diverted into a book that might strike a chord with someone in the same position."
In the book, Helen manages to hold down her job and her relationship through her often-crippling depression.
Apart from her career, she had to keep her marriage to 'Himself', as he is known on Twitter, going? Was that a worry?
"Yes, absolutely," she says. "Everything was a worry, but thankfully we're here today. Tony is wonderful and he has been fabulous, and it was awful for him in a million different ways.
"He's very level-headed – thanks be to God that one of us is. His life changed drastically, because we went from being really busy to really not busy, and suddenly we weren't going anywhere or doing anything.
"I was in the kitchen with my hundreds and thousands," she continues, "so he had to find other resources and another way to live his life. He started running and climbing, which is marvellous because it's obviously how he's having his mid-life crisis. It's much better than a red Ferrari and a 19-year-old Russian girl!
"He goes on these mad yokes, up the hills of Wicklow in the snow, and he even climbed the highest mountain in Morocco. It's serious stuff; he even has crampons and an ice axe."
As any of Marian's almost 34,000 Twitter followers will tell you, the author is hilarious on the social network, which she joined a year ago.
With a stream of funny anecdotes and observations, and a pithy turn of phrase, she has become the quirky hashtag queen and has a devoted following.
She has even ended up in Twitter Jail – where you are banned from tweeting for a period – on a number of occasions for exceeding the number of tweets permitted in a given time span.
She regularly runs 'glitterin' raffles' (#GlitterinRaffle) for biscuits, notebooks and Chubby Stick eye pencils, for which thousands of worldwide entries are received and huge excitement is generated.
Roping in her adored niece Ema (12) and nephew, Luka (11) to help with the proceedings, the raffles are filmed by 'Himself' for YouTube. Much hilarity results.
"And after that, I have to post the feckin' things," she laughs. "The people at the post office are so nice, but they see me coming with all these boxes going all over the world, and they just want to close the place.
"It's all just a bit of fun and, even though I'm so dark, there has always been a seam of joy in me. It's definitely that part that I'm interested in connecting with. I love Twitter, and the people who make me scream laughing are the ordinary people around Ireland, because they're hilariously funny and clever."
Marian doesn't find the social-networking site impersonal, either.
"I don't go out that much now, but I get so much human contact from Twitter and I love it," she says.
"I prefer to keep it light by tweeting about telly, books and make-up, but it's the same with everything now. I don't want to be sitting down and having deep and meaningfuls about how wretched I'm feeling. I just want to have a laugh."
The other people who make Marian laugh are her beloved mum, Mary, who is "a howl", and her lively nephews, Dylan and Oscar, who are almost five and three respectively and are known to Twitter fans as 'The Redzers'.
She is one of five children herself, and while she and Tony were unable to have children, Marian says that her niece and three nephews give her great pleasure. She regularly minds them and confesses that she is an adoring and somewhat indulgent aunt.
"I really believe in using the telly and giving them plenty of sugar when they're here," she says. "Not having kids myself, I don't know what the right thing to do is, and I'm only their auntie. They can do what they want when they're with me."
These days, Marian has more good days than bad, and says she feels mortified even saying that when so many people are suffering so badly because of the recession.
"I've been blessed with so much, and am aware of how lucky I am despite not always being well," she says. "I feel terrible that so many other people are suffering in different ways, and are really eroded by it."
She doesn't do interviews or book publicity – this is the only Irish interview she has done since the breakdown began – and eschews appearing on TV or radio, although she used to pop up on them regularly, fizzing with fun and mischief.
It's the simple things that appeal to her these days, like going for walks in the country with friends – "Someone brings sangers and somebody else brings a flask and it's all very retro".
And even though she'd never go to a home game, Marian and Tony love travelling to Ireland's away matches, which she says are huge fun.
"I like simple things, like going to the pictures, visiting my mother and make-up," she says.
"The funny thing is that, as a feminist, I feel conflicted about loving it, but I am so interested in hair and nails and all that kind of thing."
Looking back over the past few years, Marian says that she doesn't buy into the orthodoxy that everything happens for a reason. She also believes that people should be allowed to feel that they don't have to be stronger and better as a result of a trauma.
"My truth is that what doesn't kill you makes you weaker rather than stronger, although it makes you wiser," she says.
"I think there is pressure on people to turn every negative into a positive, but we should be allowed to say, 'I went through something really strange and awful and it has altered me forever'.
"I am definitely different. I'm less resilient, have less stamina and am far more fragile today. Maybe I won't be in four more years, who knows?
"I really would have preferred to skip the past three-and-a-half years, and just want to say to other people going through things that you shouldn't have to feel that you have to be stronger at the end of a shitty experience. Feel weaker if you want, and feel angry that it happened to you. It's okay to be scarred."
For Marian, one of the most surprising aspects of her recent depression was that it happened to her at a point in life when she thought that everything was settled and secure.
"At the risk of sounding like Ronan Keating, I've come to realise that life is definitely a roller-coaster," she smiles. "I had always thought that if I worked hard enough and long enough, I could finally put all of me in a box and place it on the mantelpiece and it would be safe.
"I thought that nothing would change ever again, but I've come to see that while you might get periods of stability, the only constant in life is change."
She adds: "It's like surfing, where all you can do is try to change direction and read the waves to stay up for as long as you can."
'The Mystery of Mercy Close' is out now in paperback
(Penguin, RRP €9.99). See mariankeyes.com. As part of the Penguin campaign for the book, Marian invites people to share their 'Marian Moment'– a happy moment
– on Twitter via the hashtag