Overdrive is one of my favorite apps. If your library offers digital books, this is the app you have to use. For those using a Kindle, you check out books through Overdrive using your library account information, then it takes you to Amazon for the downloading process. It is quick and easy.
In my area, there are other communities nearby with reciprocal agreements in place so that residents in one town can get a library card in the other town at no charge. Because of these agreements, I have access to the digital catalog of others cities in addition to my own. It is a great way to save money without feeling deprived.