The Afterparty by Leo Benedictus – review

Strap yourselves in, postmodernism fans. This is a book within a book, based on a true story. Well, not true-true. That is to say, the true story that is fictionalised in "The Afterparty" (the book-within-a-book) isn't actually true: it is a figment of the imagination of the author of The Afterparty (the book under review here).

The author of The Afterparty is the Guardian writer Leo Benedictus. The author of "The Afterparty" is called William Mendez – we know this because The Afterparty consists of a series of draft chapters from "The Afterparty" emailed by Mr Mendez to the agent he hopes will help to get it published, and the correspondence surrounding them.

The thing is, William Mendez isn't actually called William Mendez. It's a pseudonym – and because of the difficulty this presents in attending meetings with publishers, "William" ends up arranging for a Guardian writer called "Leo Benedictus" to pretend to have written the novel himself. After that, things start to get a bit complicated.

The first thing I was put in mind of as I read this was the luckless protagonist of Martin Amis's The Information, whose unpublished novel has "octuple time schemes and a rotating crew of sixteen unreliable narrators". Far from being unreadably mired in literary theory, though, The Afterparty – Benedictus's first book – is a blast: a pacy and amusing satire of celebrity shenanigans, wrapped in glittery postmodern sweetie-wrappers.

It tells the story (well, "The Afterparty" tells the story, its multiple third-person viewpoints marked out by different typefaces) of the ritzy birthday party thrown in a London club for Hugo Marks, a film star who seems part Bill Nighy and part Hugh Grant.

Hugo is a melancholy figure. His supermodel wife, Mellody, is having it off with a scruffy young pop star and, after a futile session in rehab, is returning to coke, weed, ketamine, junk etc with ferocious gusto. At Hugo's party are a lot of glamorous real people from the real world – Elton John and such like – as well as fictitious people such as Calvin Vance, a recent X Factor winner with a silly haircut and a single in the charts.

Also at the party is the novel's luckless antihero, Michael. Michael is a civilian – an Evening Standard sub who has sneaked along on someone else's invitation in the hopes of getting a diary story. Benedictus, or "Benedictus", or "William", or whoever, writes feelingly and accurately about the hellishness of being a diarist at a celebrity party.

The kicking-off point of the plot is when Hugo falls into conversation with Michael. Sick of the usual entourage of hangers-on, he takes a shine to this nobody and asks him back to his house for the afterparty. There then unfolds a series of unfortunate events involving hard drugs, very good whisky, a dead body and a lot of police and tabloid journalists – with hapless Michael (Michael fits the word "hapless" as others would a Savile Row suit) mixed up in the middle of it.

As The Afterparty goes on, it starts to look like "The Afterparty" may be a roman à clef. Could "William Mendez" have more than just a literary interest in getting his manuscript out there – and be more invested in the true-life tragedy on which his book is based than he's letting on?

As we ponder all this, we get cameo pleasures: a splendid couple of pages of dialogue about somebody having sex with a sheepdog ("Was it a female dog?" "Of course it fucking was! I wouldn't fuck a boy dog, man!"), some fine descriptive writing ("one of those very Californian women... beneath her patterned smock... the dwindled bulk that might result from being rapidly inflated once (by disease? by grief?) and then let down again, leaving a body grooved with tawny corrugations, like a sundried Mama Cass") and some enjoyably silly jokes.

Benedictus's novel-within-a-novel trick is, cunningly, almost review-proof. How good a writer is "William Mendez" supposed to be? I think Benedictus is being puckish rather than conceited, for instance, when he has his fictional agent comment on the first few chapters: "I think this is marvellous. Stylish, funny, inventive..." And where William's novel seems overwritten or awkward, how are we to know that is not Benedictus writing in character?

We know "Leo Benedictus" thinks "William"'s book is great: "I love the book – honestly." ("William" reciprocates, praising "Leo"'s "hilarious" review of a book about penises in the Observer.) But Benedictus is keeping his counsel, so I guess readers will just have to make their own minds up.

I might add that this review was going to be a lot more unkind, but I bunged Benedictus 10% of my fee to review it under the name "Sam Leith". "Sam Leith" liked it a lot.

Sam Leith's first novel, The Coincidence Engine, is published by Bloomsbury in April