You really haven't lived until you've read Christian reviewers take on Martin Amis by way of John Gardner.
What of the novel's other putative problem: its explicitness? Some of Amis' observations, for which the novel is a prop, have to do with what he supposes is a natural male instinct to possess: thus a father's (Xan Meo's) protectiveness, when certain socialized barriers evaporate, can become pedophilia, a rage to possess. It's an interesting argument. Should a famous author be socially sanctioned, then, when he explicitly describes a character's pornographic thoughts about a toddler-aged daughter to make these points? I don't see how anyone could be titillated by these scenes—though the thing with perversion is that one never can, unless one shares the perversion—but what's less in doubt is that few readers will want to read them, or feel that Yellow Dog is a literary experience singular enough to merit the revulsion.
When John Gardner was in a somewhat more temperate mood, he revisited some of On Moral Fiction's arguments in the subtler, more positive The Art of Fiction, a handbook for aspiring writers. There he argues that the novelist ought to think twice about portraying anything in her fiction that the greatest writers—Chaucer, Dostoevsky, Tolstoy, the authors of the Bible—would avoid. It seems a decent makeshift rule for avoiding the trivial (all those scenes Philip Roth sets in the bathroom) or the morbid; after all, there's little in the range of human experience that even the Bible evades. There is something private in human sexuality, something that makes it unportrayable; the very act of observation distorts, as Wendell Berry has argued. In a novel that is occasionally eloquent on the dinginess of a culture of primped, prompted, scripted, and exposed sexuality, the portrayal of actual relationship—the love that we are told develops between Xan and Cora, and between Russia and Xan—seems to elude the author, and his characters' personalities fly right out the window with it.
To be fair, reviewer Philip Christman (and just how convenient of a moniker is that?) seems to know Amis' oeuvre - and its flaws - rather well. But, ya know, we're kind of fond of Roth's bathroom bits.