Hi,
I wouldn't recommend buying a Psych textbook as many upper years have told me it isn't really necessary.
As for the rest, feel free to scout through the MacInsiders marketplace or Titles, the main bookstore in the basement of the Student Centre.
Jeremy Han (an Insider Agent on MacInsiders) recently wrote an article regarding used books. It may help to check it out.
We also avoid posting requests and ads for books on the main website, we do that in the marketplace to avoid filler content
Thanks and good luck
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http://www.macinsiders.com/showthread.php?t=2368 6)