Savers has really spruced up their used book area... The prices are higher, but there's usually a book or two I buy on every visit.
Good will seems to be getting out of the used book business. They hardly have anything on their shelves any more. But if you do find something the price is really cheep.
Garage sales are really hit or miss. I hate it when they have all their books in boxes and on the floor. I'm getting too old to lean over and try to read books that low to the ground.
Best place I've found for used books is the Friends of the Library book store.
Of course if you only read "New" books, there is always Costco for some good prices.