Hey Menzies!
Welcome to MacInsiders, thanks for posting. And great question.
You hit the nail on the head when you mentioned how it might backfire... it's true. You DON'T want to be buying books yet. Mainly because the book list is not out yet, but even when it comes out... there is no rush to buy books. I'd wait until your first day of class especially for electives you took, because sometimes you don't need every book on the book list for each class, and also remember... you might not like the elective class you're in and want to switch out of it during the add/drop period (where you can go back into SOLAR and change your elective, drop a class you didn't like and take a different one). And if you do that, you're stuck with a textbook you now don't need.
The only real advantage to buying early, is that the textbook store has a limited number of USED textbooks that they sell, and sometimes they can run out of those used textbooks for popular classes.. so then you'd have to look on MacInsiders or FB to find used, or buy the higher priced new book from the bookstore. But that scenario is usually not often, since there's normally lots of used textbooks available on MacInsiders Marketplace.
See this article for more tips:
http://www.macinsiders.com/forumdisplay.php?f=18 9
