An extract from Umberto Eco‘s This is Not the End of the Book published in The Guardian on 22 May 2011:

There are more books in the world than hours in which to read them. We are thus deeply influenced by books we haven’t read, that we haven’t had the time to read. Who has actually read Finnegans Wake — I mean from beginning to end? Who has read the Bible properly, from Genesis to the Apocalypse?

And yet I’ve a fairly accurate notion of what I haven’t read. I have to admit that I only read War and Peace when I was 40. But I knew the basics before then. The Mahabharata — I’ve never read that, despite owning three editions in different languages. Who has actually read the Kama Sutra? And yet everyone talks about it, and some practise it too. So we can see that the world is full of books that we haven’t read, but that we know pretty well.

And yet when we eventually pick them up, we find they are already familiar. How is that? First, there’s the esoteric explanation — there are these waves that somehow travel from the book to you — to which I don’t subscribe. Second, perhaps it’s not true that you’ve never opened the book; over the years you’re bound to have moved it from place to place, and may have flicked through it and forgotten that you’ve done so. Third, over the years you’ve read lots of books that have mentioned this one and so made it seem familiar.