Give them credit. Whoever dreamt up Waterstones' greatest 100 books of the century pulled off the neatest marketing wheeze since Prima persuaded Cherie Blair to edit their mag. Neat, because yesterday everyone who had any interest whatever in books found themselves unable to avoid discussing the merits and demerits of their list.

Over breakfast we asked each other how many we'd actually read (and then tried to work out if our partners/lovers were cheating). Over lunch our Eng Lit friends wondered how on earth Trainspotting could appear in the top 100, never mind the top 10 (and we thought, how can you be so pompous?). At supper the parlour game played on. Surely at least one Hemingway? No Conrad? Or Faulkner? What about The Golden Notebook? The Naked and the Dead?

As Mark Lawson put it yesterday morning on Radio 4, this top 100 was a satchel and rucksack collection. In one way or another most of the books chosen by Waterstone's customers fell into the category of juvenile cult favourite (The Lord of the Rings, The Catcher in the Rye, Dune, Zen and the Art of Motorcycle Maintenance, anything by Stephen King) or obligatory examination texts (1984, Animal Farm, To Kill a Mockingbird, Lord of the Flies). The rest were books that everyone knows are important but most have not read (Ulysses, Remembrance of Things Past). In fact, the list was a monument to the power of adolescent conformism and GCSE syllabuses.

My first response on scanning it, therefore, was a sort of sniffy disdain. Let's be honest, most people who think they are half-serious about literature are bound to react caustically to a league table that places Delia Smith above Richard Dawkins (though you could argue that the former has more encouraging things to say about the purpose of physical pleasure). And you have to be semi-suspicious about any judgement that clusters child fantasists such as Kenneth Grahame, AA Milne, CS Lewis and JRR Tolkien among the top 30, or one that regards Jurassic Park and The Horse Whisperer as even mentionable in respectable company.

But that's not the point. What makes the list so fascinating, so talkable- about, is precisely its banal, eclectic, barmily accurate summary of what would probably appear on an averagely educated, averagely middle-class shelf in a not-very-bookish home. It does, in fact, reflect what people really read.

There's an additional value to a list like this. Ask yourself, how many of those titles are books (such as The Master and Margarita) that you thought you knew about, but have never in fact read? Weren't you reminded of books, such as A Suitable Boy, that you never got round to reading but meant to one day?

Ten years ago this list would have been very different; in 10 years' time it will be different again, if only because The Horse Whisperer will by then be long forgotten (thank heaven). But it is no less intriguing for that.