To be honest, I prefer charity shops to professional shops for 2nd hand books.<p>That said, I still visit professional shops rather more than I should (it depends on the shop.)<p>Of course charity shops are cheaper, that's part of the appeal, but I have more success in them because they are less discerning.<p>Over the years I've acquired a LOT of books, so now I tend to limit myself more. Mostly I now collect science fiction, with an emphasis on work pre 1970. These were made cheap, and are usually in "poor" condition now.<p>Professional shops won't shelve them, whereas charity shops will, so I have more success there.