It depends on what type of course you're doing. Some use more books than others; some less but more expensive. Some you can get by without buying anything at all.
Engineering will probably cost you a couple of hundred in books. From what I've heard, it unfortunately seems to be one of those courses where textbooks are pretty much necessary.
I've been told not to get the textbooks unless the professor/lecturer is bugging you to get them... because what's in a book can be found on the Internet.