True to its title, Belinda McKeon's second novel is a tender account of a girl's coming of age in the Dublin of the late 1990s, of her bitterly-won discovery that friendship can be irreconcilable with sexual passion, and of how love can become so proprietorial and demanding as to turn into a destructive obsession.
And that the object of her obsession is a young gay man who started out as her best friend makes her developing feelings about him all the more unsettling both to her and to him, while her behaviour towards rivals for his affection becomes all the less rationally defensible.
When we first meet 18-year-old Longford-born Catherine, she has just embarked on an art history and English degree in Trinity College and she's in Co Leitrim, in the family garden of James, an aspiring young photographer whom she's recently met courtesy of her Baggot Street flatmates.
The reticent Catherine and the exuberant James have rapidly become the closest of friends, utterly attuned to each other's thoughts and moods. When it later dawns on her that James is gay, the realisation only deepens her love and concern, even to the extent of trying to locate suitable sexual partners for him.
All of this - not least the intensities and confusions of youthful alliances and yearnings - is beautifully evoked, as is the Dublin of the time, a city of seemingly unlimited possibility and promise for the likes of Catherine, James and their circle of friends.
However, when Catherine even more belatedly realises that her love for James has also become sexual, and when James somewhat desultorily succumbs to her desires, the book becomes less persuasive, both psychologically and emotionally. It's as if the author hadn't quite managed to square this sudden development with what she'd already given us to understand about these two people - which didn't include the likelihood of them having a sexual relationship.
And when that aspect of the relationship is ended by James, who after all is homosexual and seeks fulfilment from other men, the book becomes darker, with an increasingly distraught Catherine becoming both jealous and petty and finally vindictive. Yet it's a measure of our empathy with her that even when she behaves hatefully, our concern is at her need to do so.
Everyone has their reasons, Jean Renoir said in The Rules of the Game, while in The Philadelphia Story we're reminded by Katherine Hepburn that "the time to make up your mind about people is never". McKeon would undoubtedly agree - one of the abiding qualities of this novel is the author's refusal to pass judgment on any of her principal characters, no matter how callow some of them might be in their actions and observations.
This was evident, too, in McKeon's award- winning first novel, Solace (2011), in which her concern for human frailties and failings - and decencies, too - was striking. It was an honest book and honestly written, with none of the stylistic attention-grabbing that's sometimes encountered in Irish fictional debuts.
This second novel is just as unshowy and is even more poignant about the fragility and transience of human relationships. In a couple of set-pieces, it's funnier, too.
There's the jittery, almost unhinged interview Catherine conducts for Trinity News with a mockingly patronising Irish novelist, and there's a bravura extended sequence at a party in the same gentleman's mews house, at which an Irish Times woman journalist is gleefully skewered by the author.
Perhaps she's as fictional as the book's other characters, though in a recent interview the author acknowledged that this new novel was "autobiographical at its core". And certainly McKeon, who now lives in Brooklyn and teaches fiction at Rutgers University, shares some characteristics with Catherine: both are from rural Longford and both were of the same age when studying at TCD in the late 1990s.
In the book's coda, though, which is set in the New York of 2012, we learn that, unlike her creator, Catherine has opted for a different kind of writing career. It's an affecting end to a book that has beguiled us from the outset, though this reader's patience was occasionally tested by Catherine's frequent encomiums to James's unique qualities, not least his talent for "reducing her to helpless laughter with his jokes".
She has to be trusted on that. Indeed, the reader never quite sees in him what Catherine does, while it's also possible to wonder why so much is made of the social trauma of being gay.
Yes, the marriage referendum may be 17 years in the future, but this is 1998 after all, five years after homosexuality was legalised and a time when many Irish gays, especially in Dublin, were much more at ease in their sexuality than the hapless James. Why he should be so uptight and fearful, especially among approving friends, isn't really made clear.
But these are just quibbles about an absorbing and immensely likeable novel that merits being placed alongside such other coming-of-age fiction as Elizabeth Bowen's The Death of the Heart and Françoise Sagan's Bonjour Tristesse.
Picador, hbk, 448 pages, €14.99