Best E-Reader in the Market?

It would help if you listed some criteria.

  - Purely for reading? (Don't care about pens or drawing)
  - Desired size? (10 inch? or 7 inch?) I find 7" too small for textbook PDFs.
  - Android support? (Being able to install Firefox with an ad-blocker is nice)
  - Libby support required? (For borrowing books from the library)
  - Back/front light required?
  - Budget?

I'm considering the Boox Go 10.3, but I'm waiting for more reviews to come out. (10.3", Android support, no light, comes with pen)