This is a terrible book, almost too terrible to read. But, in a country racked by the suicide of young men, what Welch has to say is necessary, courageous and encouraging.
Egan Welch, the author's son, died by drowning in 2007. He was 27 years old, handsome, intelligent, successful, addicted to alcohol, uniquely self-destructive.
The uniqueness is startling. The fury and speed of Egan's advance on death are unlike anything I have ever come across in life or literature.
At the age of 21 Egan was working for the University of Ulster at Coleraine and also running a graphic design website company. In his first year of business, for example, he made a clear profit of £60,000 (€74,000).
He was personally lucky, too. He was engaged to be married and all his life he was much loved by his four siblings, his mother, manager of the Citizens Advice Bureau in Coleraine, and his Cork-born father, a respected academic and an outstanding poet.
Given how fortune smiled on him, it is hard to comprehend Egan's fate. How could his father explain, for example, his son being found in the attic of their family home, so helplessly drunk on three bottles of vodka that the fire brigade had to be called to stretcher him down a ladder?
On another occasion, shortly after Egan was detoxed and apparently rehabilitated at John of God's in Dublin, he suddenly went berserk, smashing windows with his fists.
Long after that incident Welch found above the door into his study a drop of his son's dried blood. "I have left it there," he says, "and will never clean it off."
Drink was the demon, but there were other devils attacking Egan. Throughout Ireland there is a baleful underworld, fuelled by alcohol, drugs and violence. In the North the menace is fed by sectarian hatred.
One of Egan's friends was kicked to death by thugs, including a number of girls, in Portrush, near Coleraine. When they got out of jail a couple of years later, they swaggered around the town "half-proud of what they had done, enjoying the reputation".
Shortly after their release, and probably in reaction to that legal injustice, another of Egan's friends plunged from a cliff. Egan was hard hit by these deaths. He had, as his father shows, a Christ-like ability to share in the suffering of others, but he also felt a need to be punished for that sharing.
Egan tried to commit suicide in 2006. The note he left included the sentence: "If I die it is not alcohol that killed me, it's something else." This book tries to analyse what that 'something else' could be.
There are many young men as troubled, if not as brilliant, as Egan Welch in Ireland. This book makes a significant contribution to understanding their crisis.