Great Apes is an idea-novel, its opening a partial sequel to the Self-parodying media politics of recent novella, 'The Sweet Smell of Psychosis'. Artist Simon Dykes is on the cusp of a new show. The unseen canvasses are big, disturbing, different in tone and texture to his prestigious World of Bears; guarantied column inches. Life is a Prozac-hazed social-schmooze of openings and crap coke in the club bogs of the fashionable Sealink, then back to the girlfriend's for an energetic shag. Only, what happens when you awake from your night of passion to find not your beloved beside you but a fully-paid-up monkey?

You go humanshit.

If you're Simon Dykes, at least. The hospital rushes you in. There's a nest in the corner and everyone comes knuckle-walking to see you. Your doctor is a monkey. Your sexually voracious girlfriend is now a sexually voracious chimp. Your agent an ape. The world you know is peopled by primates.

This is Self's idea, to be intellectually worried into life. Simonkins is helped in his struggles by the aging and illustrious Zack Busner - Self's own Oliver Sacks - originator of the infamous Quantity Theory of Insanity. Busner sees glory and guilt in restoring Simon's chimpanuity: the ape who mistook his patient for a reputation.

The author is long in synthesizing this world. Apes still drive Volvos, watch Masterchef and adorn walls with the 'pronounced eyebrow ridge' of Liam Gallagher. Racism - boboboism - is subtly rife, and sexual etiquette turned on its head: 'Oh, Reverend...your arseholiness is so beautiful, your spirituality gushes like spunk from your cock.'

Sometimes it feels as though the book is wearyingly about nothing but the promiscuous presentation of the 'ischial scrag': the celebration of speed as a sign of virility ('I want a lover with a fast hand/I want a lover with a rapid touch'); the active promotion within ape patrols of peadophillia and incest. His research is meticulous.

For all his rigour, mind, anyone who has read much Self must surely conclude that he's a sucker for a bad joke. Many an Observer column loosed-off a thousand words towards a consciously cringe-making gag, and novel or no, more than a few are scattered through these 404 pages (Lloyd Grosschimp and Anton Mossichimp, anyone?) But it is also, of course, so dexterously written that even the eventual ennui we experience is sidelined by Self's celebration of language: a painting of crash passengers, 'being tossed...into a heavy salad of death'; a boat rowed past a window, 'slid into the grey concrete like a vast hypodermic powered by eight hearty junior doctors.'

Self is blessed with what he calls the 'intellectual armoury' to marry media-millenalist-hip with honed eighteenth-century satirical technique. 'The cumulative effect, for a straight person, is like having the vicar come round and shit in your teapot.' What Great Apes lacks is the spiteful narrative drive of My Idea of Fun, although it does introduce a bittersweet, even moving quality to Self's writing.

A couple of years back he appeared on Radio 4 vigorously (and hysterically) defending King Kong to Melvyn Bragg. Up to your neck in Great Apes, you do have to start and wonder if such a short form mightn't provide this self-styled 'Joanna Trollope manque' with his best platform. Much too long, here's a very good book aping a potentially great one.