We use Kobo. I borrow as many epub books from the Public Library as I buy from Kobo. It is much like borrowing an actual book. They have a limited # of ecopyrights they have purchased and sometimes you have to wait for a copy. You have it for 3 weeks, then it disappears. If it is an old book, in the public domain, copies are not limited.
No problem downloading in the U.S. and when we have encountered problems I have found Kobo easy to contact & deal with.
Bought a Kobo Glo HD today for $119. at Chapters Indigo. If you buy, get one with the screen that will light such as the Glo or Aura. Great for reading outdoors in the bright sun and later the screen can be lit when too dark. Aura is also available in a waterproof model.