Of course they won’t have heard of every single one, but anyone who is attuned to the world of contemporary publishing or books is going to have come across some, even the debuts, as they’re often mentioned in terms of auctions in The Bookseller, and it’s really not realistic to find judges who know nothing about the book world, but who are still prepared to read a long list of 150 or 160 books over six or seven months and then enter the fraught process of choosing a shortlist. I mean, I don’t think providing the judges with anonymous copies is going to mean there is a ‘pure’ vote.
Which is not to say that book prizes aren’t pretty problematic in many ways. A friend has judged several biggish ones (not the Booker), and from what I gather, it’s all too easy for something all judges feel ‘meh’ about to win, because often four judges will be passionately arguing for four different books to win. When it’s clear no one is budging, and it’s a complete deadlock, a fifth book everyone agrees is fine but isn’t that excited about wins instead.