Definitely the cheapest book store on campus. I wish Amazon was more popular/well known when I went to school, I would have saved a sh*tload on books. Oh well. I love coming here when I come back to campus - stock up on Illinois shirts - they are the cheapest here, there's always some deal. One year they were giving out packets of kraft microwaveable mac & cheese with every book purchase. Towards the end of the selling season, we saw boxes there, and they just let us take a box home :) But if you want free stuff, the Illini Union book store always has nice big boxes of free samples at the beginning of each semester right outside the door by the bag check.
But cheap when they sell means cheap when they buy back...