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Recently discovered two good books stores.
Dollar Bookfair
http://www.dollarbookfair.com/
In the Laguna Hills Mall
24155 Laguna Hills Mall, Laguna Hills, CA 92653
Good used bookstore. Most titles in the $2-$3 range. Large selection of mystery and science fiction novels.
Book-Off
http://www.bookoffusa.com/
In the Del Amo Mall (two locations in mall)
21712 Hawthorne Blvd # 290, Torrance, CA 90503
Good selection of business books, with used books at reasonable prices.