I think half the fun of a used bookstore is the treasure hunt. This used bookstore is better organized than some of my old haunts in Dallas but I will survive.
I think of used bookstores similar to looking through your Grandmother's attic at her book collection - it isn't supposed to be all shiny and new.
Bookman's has a decent selection of books, I've found an entire collection of Rishdie one afternoon! Of course it is always going to be a crapshoot but that is just the way it is in used books.