In regards to the tablet, I’m thinking about buying an Amazon Fire HD 8 though I’m open to any and all recommendations.
As for the distro, I’m fine with Ubuntu or Linux Mint (or for that matter anything that you may recommend).
For the ebook reading software, I’m leaning towards using Foliate since it supports kindle, epub, and pdf formats, not to mention that the UI is great and intuitive.
Having tried and failed miserably with Linux tablets a number of times I don’t think they’re quite there yet
As much as Amazon suck my old Kindle has always been pretty nice to use (the OG e-ink ones not the android ones, if you’re looking at the kindle fire just look into buying a better android tablet)
There’s also the ReMarkable, I believe that also works as an e reader with the added benefit of the pencil to take notes with (worth looking into yourself I’ve never owned one)