I've worked in used bookstores for many years, and I want to tell you what every used bookseller in Chicago already knows: Bookworks is the best possible place to sell your books.
Now, Bookworks buys very selectively -- as they should. They will only buy books that they believe they can sell. They will only buy books in very good condition. So, it is highly likely that they will not purchase every book you offer to them. However, for what they can/will buy, they will make you the best possible offer out of any bookstore in Chicago, and you should most definitely take it.
Also, they will talk to you about your books. Once, they rejected a book I brought in that was written by a popular local author. I asked them if they were certain they didn't want the title, and then explained to them who the writer was, and why I thought it would sell. They listened to me, and offered me $2 for it (which is a really nice offer for a paperback).
Also, thanks to their careful curation, their selection is truly great. So it is the best place to shop, as well as sell. The staff is very friendly, unpretentious, and kind. It's not easy to find that kind of help in used bookstores these days.
Stacey S Chicago