This is a complete reimagining of the Open Book Project, but the original mission remains:
As a society, we need an open source device for reading. Books are among the most important documents of our culture, yet the most popular and widespread devices we have for reading are closed objects, operating as small moving parts in a set of giant closed platforms whose owners' interests are not always aligned with readers'.
The Open Book aims to be a simple device that anyone can build for themselves. The Open Book should be comprehensible: the reader should be able to look at it and understand, at least in broad strokes, how it works. It should be extensible, so that a reader with different needs can write code and add accessories that make the book work for them. It should be global, supporting readers of books in all the languages of the world. Most of all, it should be open, so that anyone can take this design as a starting point and use it to build a better book.
Check out the promo video as well:
https://youtu.be/vFD9V8Hh7Yg
There's slowly starting to be more options for this. The reMarkable devices seem pretty good, but they're a little pricey (though, I'm pretty sure they're not owned by Amazon, so it might technically fit your requirement).