Whenever I'm in Hay-on-Wye either for the literary festival or simply for a lovely day out I always head straight to Richard Booth Bookshop. With its mixture of second hand alongside brand new books, its the eclectic mix that always keeps me coming back. On my last visit I managed to pick up a beautiful second hand edition of Jane Eyre. The range of non-fiction is also very comprehensive and I find their book tables a great way to discover titles that may have typically missed my attention. They have some great events on during the Hay Festival and they even have a cinema which often screens NT Live performances.
If you buy one book:
Richard Booth's is an absolute treasure trove of second hand books so it's pretty difficult to suggest what to pick up as the stock can be pretty varied visit to visit. Top of my list every time I visit are any classic orange Penguin editions - I've managed to pick up a couple including one by Katherine Mansfield!
44 Lion Street, Hay-on-Wye, Hereford HR3 5AA