The other reviewer, Jessica Goette, has outlined the plot really well, so I won't bother getting into that. I will just add why I think I didn't find the novel as funny or worthwhile as she did.
The main character, Bruno Dante, is a sleazy guy, and I think the author wants us to find him funny. But sleazy guy humor only really works if the sleazy guy is undeniably, hilariously funny; I'm thinking of Rabbit Angstrom from John Updike's novels, the gang from It's Always Sunny in Philadelphia, and the character Kenny Powers from Eastbound & Down. Actually Kenny Powers is exactly who Bruno Dante wants to be but most definitely isn't. Every now and then he'll say or do something funny, but it's rare.
The novel is just too mean spirited to be funny. The first chapter alone includes pedophilia, incest, public masturbation, disturbing violence, and several other things I would describe except I don't know that Amazon's censors will let me.
Without a consistent sense of humor, Bruno Dante is an extremely unsympathetic character. The author tries to have it both ways by making Dante a failed poet, a sensitive soul hidden under layers of rage and disappointment. I found this aspect of the novel pretty weak and unbelievable. Especially ridiculous is when Dante takes up with an underage prostitute who shares his taste in literature. Really? A sixteen-year-old hooker in L.A. shares a middle-aged professional poet's appreciation for e.e. cummings and William Faulkner?
And yes, the main character does some maturation, does actually progress through something of a plot. But only just a little bit, and ultimately not enough to make this a worthwhile read.