Kelly--As Dreams suggests, the various libraries all have what ever overdrive books they decide to pay for.
On the Overdrive page for each library, you can click on "Advanced Search" and it'll take you to a search engine. On that page, only change the format type to either "Adobe EPub" or "Adobe PDF" and choose "Search". That'll bring up all of the books that library has with that format type. Right now, when I look at the San Francisco Library collection, I find 478 ePub books compared to only 108 at Contra Costa County library.
The New York Public Libary doesn't currently offer ePubs, but they do have over 12,000 PDF books available. (That's why I felt it was worth $100 for a one year membership!) I'm also hoping they add ePub in the near future--they seem to add books to their collection quite frequently.
I find that most of the libraries I belong to add a few new books every month or so. I've been disappointed with the Northern California Collection though, because they haven't added anything new since August or September of last year.
Another thing I find useful is the search engine on Overdrive's site: search.overdrive.com . You can type an author or name of book your interested in and search on it. It'll bring up all the books by that author or with that title name and list which libraries the books are available at. This is super useful if you belong to several libraries, because you can search them all at once.
Hope this helps!
dordale
