[adriand]

Honestly, I have no idea, like I said it's really old. It's waterproof, so maybe an H2O? I don't think you can really go wrong, although take a look at online reviews before purchase. Mine is fairly small (like small paperback dimensions), which I thought I might not like, but in practice it's never been an issue and I like the portability. And the battery life is great, I read a lot and I can go weeks without charging. Another bonus with them is that they support non-DRM ebook formats, so if you have books lying around you can just transfer them to the device.

In terms of Libby support, keep in mind that the method I am talking about doesn't depend on any interaction between the Kobo and Libby. I think it's all based on Overdrive, that is, I check books out from the library, and the Kobo knows what I have checked out and syncs anything that isn't on the device already. My kids have newer Kobos and this method works well for them too, so you should be good.