Book transfers are supported by the device itself, no extra software required. It genuinely acts as a USB thumb drive once permission to give access to the PC is allowed on the device, similar to an Android phone. Once a book is put onto it and it’s unplugged, it will automatically find the book and add it to the library screen.

The h2o model is also waterproof, which was a unique feature at the time, while the new Kobo models are all waterproof.

Should be, yes.

I use a Kobo Libera h2o (which I think is discontinued now), and I’ve been extremely pleased with it. Kobo doesn’t lock down the device, so transferring books to it is as simple as plugging into a PC and pressing a prompt that allows it to be opened like a thumb drive.

Personally I would recommend any of the Kobo devices, which appear to all be waterproof now as well.

ePubs are generally a bit smaller than PDF’s, and more critically, allow the text to reflow to fit the screen of any device, or to your personal preference (such as spacing, font size, ragged edge vs full justification, etc). It’s the best open-source format for reading on a device, IMHO.