Initially I had my Samsung Tab S doubling as my e-reader. But as a reading device, Kindle I think as best and now using Kindle Voyage only as e-reader.
I read my books on KOBO ereader. I have had the device for more than 4 years. Very recently I have got a new KOBO Clara, which is the latest version, in HD. I am more than satisfied.
When I first started reading ebooks, I did it on my mobile (Nokia 6681, N95 ... man, I really was reckless with my eyes!). Now, its Kindle for ebooks, for about 5 years now and iPAD/HP Stream Windows tablet for PDF and comics (CBZ/CBR).