Another great place to buy books inexpensively is Strand Books in New York. It is an old style bookstore with very tall tightly spaced shelves packed with used books. The store looks cluttered but I have made some amazing finds in there. I literally spent an entire afternoon just going through their history section (and I was selective about which countries I looked through). Their prices are very good and as an added bonus they sell reviewer copies of all the new books at 50 percent of the cover price. It would probably take a full day to go through that section alone. They have a website now that allows purchasers to search their collection. Their saying is "eight miles of books" but the major downside is I always buy more than I will probably read.