Kobo Clara 2e - I find it a bit sluggish, some other convos here tell me to use KOReader for a better experience.
I used to have a Paperwhite 3g, fantastic device but even offline I can't caution that business, their ethos and practice's. Fuck Amazon.
My kobo makes it easy to sideload books even without Calibre. Upon buying from your e-reader, the store will send you drm-free books if that's the publisher' request. If you bought a drm-encrypted book, and you need or want to read your books elsewhere the current adobe DRM protection is easy to remove with the obok plugin from the DeDRM Calibre Plugin Package, making your book truly yours.
(Removing it from the kindle books is becoming increasingly complicated)