One of the things that excited me most about getting an ereader was the idea that I could check out books from the library without having to go to the library.
But it turns out that ebook lending systems in public libraries are not as idyllic as imagined. Every book available in paper is not necessarily available in electronic form. And although transmitted through the interwebs, you can't just check out an ebook at will. You have to wait for someone else to finish it (and when it's a newer book, you generally have to fend off the bookworm masses).
So how is your library's ebook collection? Do you actually like using it? If a paper library book and an ebook are both available, would you ever choose the printed page instead?