My local public library now provides e-books (via a consortium), and I just wandered through the maze to download my first one. I have a first generation Nook Color, so ePub format works fine ... if I can just get the book onto the device with digital rights management handled. The consortium requires me to install Adobe Digital Editions on a PC, which then acts as an intermediary between the book source and any reading devices. (ADE also acts as a reader on the PC.) A friend of mine, a confirmed Windows user, has already been through the process, so I know it works.
Adobe, like a lot of other software publishers, supports Windows and Mac OS but not Linux. <insert usual imprecations and rants> The good news is that ADE runs fine under Wine, once you get it configured correctly. The bad news is that (a) Adobe does their best to hide the fact that you can download a complete installer program -- their web site recognizes I'm using a Linux variant and tells me to sod off -- and (b) getting ADE running under Wine to recognize the Nook (connected to a USB port) is not entirely obvious.
Fortunately, when I started searching for information on the latter point, I came across the following complete, accurate and readable post by gorthx. There's no need for me to expand on it; I'm just posting the link here to help boost its position in Google (and so that I don't lose track of it).