This is the leading on-line auction site. Prices vary, as you might expect from any auction, but they tend to be low. I suggest that the other sites listed here be used to determine the market value of a given book before bidding at eBay. The site employs several mechanisms to discourage fraud, including a sophisticated rating system based on feedback from both buyers and sellers. This web site is dedicated to connecting military book fans with dealers all over the world.
Prices are mixed but tend to be on the high side.
Provides access to a huge selection of books, all on military-related topics.