Saved myself $50 on 2 books from this...Hope it saves you money too :)

Textbooks can be outrageously expensive if you don’t look in the right places. TUN, the discount-finding service for college students, recently launched a textbook search engine that scours thousands of book sellers—including Amazon and Chegg—for the best deals on new and used books.

http://lifehacker.com/tuns-textbook-search-engine-compares-prices-from-thousa-1724919075