After my first semester of College, and I noticed that I would never use the books again (except Psychology), I find it a waste of money. But of course, I sold them back to the school, but only got 40% back. So now I just go on chegg, and rent books for the semester. Saved me about $850 total for 3 semesters.
But if you are getting books online, make sure you find out what books you need, and get them before the semester starts. Chegg will take about 5 days - 2 weeks on average, for me at least.