I did an e-reader teaching clinic last week and the best one that anyone brought in was either the Kobo or the Sony.
I absolutely do NOT recommend the Kindle because not only is it kinda ugly, more importantly, Amazon REFUSES to allow library e-book downloads for it (which is imho, jerky!).

TL:DR - Kindle BAD. Sony or Kobo GOOD

Full disclosure: I have an iPad myself.