If you have to buy books, check if you can buy it used: Used books do not quite give the same feeling as leafing through the crisp pages of a brand new book.
But considering that you can get used books for almost as much as half the price of a new book, it is a small price to pay.
Check if you have a used book store in your city.
For text books, look online on bulletin boards, mailing lists etc, and price compare on websites.