As it happens, the used bookstores all over Michigan and Detroit in particular, are great places for finding books about numismatics. I have lived in and around Detroit and Central Michigan, as well as central Ohio, Cleveland, the Space Coast of Florida, and Albuquerque. Michigan rocks for numismatic references. However, almost any big city has some opportunities. Having visited New York, Louisville, Minneapolis and goodness knows how many others, I can usually find some kind of bargain, if I shop long and hard enough. Albuquerque was a challenge. The used bookstore dealers there never understood anything but "Red Books" which they refused to buy. However, one of the coin stores was pretty active in buying and selling libraries along with numismatic material, so that worked out. Libraries have annual or semi-annual "FOLA" (Friends of the Library Association) sales and at them, I have found the massive Krause Standard Catalogs for $1 to $5 depending.
I came across a 2 volume 1841 First Edition of Edward Hawkins' "Silver Coins of England" for £35... which i thought was pretty good.
I've gotten several books from fellow collectors whom I've met via internet chat-rooms such as this one. I also purchase used material on eBay. I usually buy new books at WaldenBooks. If they don't have what I'm looking for in stock, they can usually order it for me. I have also picked up a few books at the semi-annual local library sale.
I got my Breen Encyclopedia at www.brooklyngallery.com and I got my copy of Taxay at the CSNS convention.
