Your sidebar info says you're in BC, so all you need is a valid library card for any BC library, and just head over to our province-wide "
Library Without Walls" e-book/audiobook lending site.
I think we have a pretty decent selection for many books and genres, though of course if you want stuff in certain categories like sf/fantasy, there really isn't much to choose from. It helps if you like romance and thriller/mysteries and political/history non-fiction, I think.
Why not install Adobe Digital Editions if you haven't already (don't forget to register an Adobe ID so you can transfer the books later) and try borrowing a book or two? I've heard that either the Bluefire or TXTR apps for iPhone can read ADE-DRM stuff. Oops, just noticed that you were planning to try stuff out on the Overdrive app.
Hope this helps, and happy browsing!