B. and I visited Hay-on-Wye at the weekend, with a long list of books we wanted to find. We came away with a large stack of books. The list and the stack had an overlap of a couple of volumes, which shows equally how fun and how frustrating secondhand-bookshopping can be. On the plus side, I now own Kim Stanley Robinson's A Memory of Whiteness, Italo Calvino's Invisible Cities, Greg Egan's Diaspora, a stack of Pocket Canons and several more books by Paul McAuley. On the minus side, I still don't have Robinson's Mars books, Paul Cornell's British Summertime, Justina Robson's Natural History, any more books by Kim Newman or anything at all by Mark Chadbourn that isn't his Doctor Who novella, Wonderland.
Hay itself is a marvellous place -- an entire town infected by the well-established space-warping properties of large concentrations of secondhand books, so that its streets fail to meet up when they should do and the Bookshop Map (issued at Tourist Information and in the bookshops themselves) appears to bear more or less no resemblance to the layout on the ground. Some of the bookshops themselves go back for miles, taking up far more space than can possibly be there.
I don't know what Hay's history is, but it's clear that, at some point in the distant past, it passed the secondhand book equivalent of Douglas Adams's Shoe Event Horizon, since which it has been more economical to open a secondhand bookshop there than any other kind of business. What's weird is why this would have happened to an obscure, and not enormously accessible, town in the Welsh Marches. There's a short story in there somewhere, I'm sure.