Backlit e-Reader, least eye strain, & open most formats?

runswithascript

I am looking for some advice on an e-Reader, which I had intended to buy second hand to keep costs down, but I will consider purchasing a new one also if the perfect device is too new to be available second hand. The main capabilities I would like it to have are as follow:

1. Backlit so I can read at night without a light

2. Least eye strain possible. I do not suffer with my eyes, but I have read about how blue light from a regular tablet can affect sleep, and I would rather negate this as much as possible.

3. The ability to load almost all, or most formats, as I have a large collection of e-books from Amazon but also other providers etc. I am happy to root the device, if necessary.

Wi-Fi would be nice for transferring files, but this is not a deal breaker. I am happy enough with a black & white display as I want this device for reading books, colour would be a bonus, but not something I want to pay extra for, or sacrifice anything listed above.

Any advice?

runswithascript

I just watched a video about the Kobo Aura one, seems great, though pricey...