The new musical version of "The Commitments" currently playing in London's West End should be a reminder not only of Alan Parker's 1991 soulful little-movie-that-could, but also of the significant source material for both those entertainments: Roddy Doyle's debut novel, published in 1987. "The Commitments" was part of a new wave in Irish fiction: For the first time, to use poet Harry Clifton's term, the "urban voice" was making itself heard. And no one captured its blunt poetry better than Doyle.

A quarter of a century and many successful books later, Doyle still has an ear that many of the musicians he loves to write about would give their left lobe for: "She was wearin' big mittens, on her hands, like, and these wine cooler yokes, padded tubes. On her feet."

The speaker here is Jimmy Rabbitte — the same Jimmy Rabbitte who was the young entrepreneurial manager in "The Commitments." In the recession-clobbered Ireland of 2011, Jimmy is still in the music business, running a nostalgia-with-an-attitude website called kelticpunk.com. But the woman he is describing to his father (Jimmy Sr.) is not the lead singer of some far-out band from the early 1980s; it's a woman pictured in the Wikipedia article on chemotherapy. Jimmy Jr. — now 47 and a married father of four — has being doing this kind of online research because he has bowel cancer, and he is in the pub breaking the news to his dad.

It's a beautifully written and emotionally calibrated scene — one of a stack of such scenes in the first half of the novel that made me think that "The Guts" was on course to be Roddy Doyle's most substantial achievement to date, one that blended the heavy and humorous sides of life more effectively than any of his other books (although "Paula Spencer" would also be a strong candidate).

I won't say (to use a Dublin expression) that the second half of the novel left me gutted, but it did leave me unsatisfied. True, the extended grand finale at the Electric Picnic festival is a fine piece of writing. (Electric Picnic? Imagine an annual Irish Woodstock, with better traffic management.) Jimmy and a motley middle-aged crew hustle from tent to tent to catch the bands Jimmy has a vested interest in; sometimes it's business, sometimes it's personal, sometimes both.

But there are emotional elephants in the tent that the final stretch of the novel barely deals with, or deals with in such an oblique way that the reader feels shut out. Here I am not talking about the cancer but about Jimmy's relationships. An estranged brother and a couple of stars from the Commitments (the band) come back into his life, and these entanglements, which never get properly untangled, are far more interesting than some of the more contrived musical elements of the plot. The real hero of the novel is, arguably, Jimmy's admirable wife, Aoife, who gets sidelined at a point in the story when I thought she would come center stage.

"The Guts" is a decent performance, but doesn't give us the "access all areas" badge I had expected.

Robert Cremins teaches in the honors college at the University of Houston.