I got a Kindle Paperwhite as a gift from my work and I fell in love with e-readers. Then I really didn't like how Amazon was locking down getting your own epubs onto the device (it's only gotten worse), so I quickly found Kobos were an excellent device for my use case. I found that buying ePubs online was way more available than I would have thought and now I get to keep my digital books. Just drag and drop them onto the Kobo.
Kobo also has a "sideload mode" that (despite the slightly confusing name) just remove all online features all together.
Kobo also has a "sideload mode" that (despite the slightly confusing name) just remove all online features all together.