Copyright is an important idea in libraries. Copyright dictates what can be done with a work.
David Pogue of the New York Times gives his take on copyright and electronic versions of items like books from the point of view of an author:

Unfortunately, I've had terrible experiences releasing my books in electronic form. Twice in my career, 'blind' people e-mailed me, requesting a PDF of one of my books. Both times, I sent one over–and both times, it was all over the piracy sites within 48 hours, free for anyone to download.
I've got a mortgage and three kids to put through college, and it broke my heart! Unfortunately, the bad apples have once again spoiled it for everyone else.

The Library has a lot of electronic books, but they're not always easy to use and access because the vendors need to institute certain practices to make sure the material's copyright isn't violated (like no printing!). It's tough because it assumes the user is a thief, rather than just someone trying to do research. But as Pogue reminds us, there are financial implications for the author when these precautions aren't put in place.