What good is a book if you can’t judge by its cover?

For the person giving a best man’s speech, or the toast at a leaving do, there are a number of boilerplate jokes that can be adapted to the circumstances.

For instance, if you want to mock someone’s lack of erudition, here’s a gag that has been used a thousand times, and not just by me. “[Insert name here] is looking a bit sad because he had a fire last night in his personal library … and both of his books were destroyed.”

Pause for polite laughter, and then hit them with the punch line. “…and he hadn’t finished colouring one of them.”

I always thought this was a joke with a definite shelf life (pun intended). If we believe what we’ve been told,there’ll come a time soon when no one will buy books, and the gag doesn’t quite work with an e-reader. I may, however, have misjudged the march of technology, judging by the response to the novelist Alexander McCall Smith’s appeal on Twitter for suggestions about how best to order his bookshelves. Alphabetically by author or title? By genre? By vintage? Fiction separated from non-fiction? Or indeed, as one of the more unusual Twitter responses suggested, by colour.

The idea may have left some younger followers bemused, but the discussion really took off, or trended, as I believe the vernacular has it.

This is Twitter at its best: provoking a national conversation that interests, diverts and has a practical application.

Moreover, because everyone is equal on Twitter – it doesn’t matter whether you’ve got a million followers or a dozen, your tweets are still a maximum of 140 characters – the conversation is very democratic.

Mr J Public’s views are just as relevant and prominent as those of a multimillion selling author. The problem lies in the narcotic appeal of such an exchange. You can easily find yourself sucked into the debate, and before you know it an hour has passed, and you’ve not done any work.

Some literary judges might say that anything which keeps McCall Smith from writing his novels is a good thing, but I think that’s terribly unkind. Anyway, what was clear is that people still really care about books as physical objects: they like the look of them, the feel of them, and – perhaps most importantly – what they say about you. You may read only Jilly Cooper and Jeffrey Archer, but make sure you have the latest Julian Barnes, the Steve Jobs biography and some Penguin classics on your shelves.

One problem – or maybe it is an advantage – of a Kindle is that other people on a train, or a bus or on the beach can’t see what you’re reading. What’s the point of wading through a socio-political history of the Balkans if no one can see quite how clever you are?

You might as well be reading the new Alexander McCall Smith (although, on second thoughts, you might be better off with the Balkans).