Being an English major, the majority of the books I have had to read for my classes are novels or essays, those of which can easily be found at a library. Plus, most students do not want to ultimately own the books they have to read anyway. I have fully taken advantage of my access to the Monroe County Public Library. It has a wide selection, including an entire room dedicated to career development, which in my senior year now, I should have accessed a little more. Plus, it is easy to find any book you need. Their website allows you to search the book you want, even the edition your professor chose, and then hold the book so that when you go to pick it up it is on a shelf under your name. There is no searching the stacks, no contact with anyone (self-check-out), and fifteen minutes out of the day rather than money out of your pocket at the bookstore. Now I'm not against the IU Libraries entirely, however, in my experience the website is not as accessible; I always have to ask three different people in order to find the floor my book is on and whether I can check it out; and there is seldom parking convenience when all you are trying to do is run in and grab a book not pull an all nighter studying at the library.
Now if you are one of those students who has to write in the margins or your professor requires a publisher's edition of the book that no one has ever heard of, then buying may be the way to go, but for those who are as frugal as I am or do not have the funds for TIS bookstore's expensive prices just check the libraries, it's free.