[1]: https://news.ycombinator.com/item?id=9245467
I hear good things about the eink device Remarkable though.
iPad Pro (11") with Scrivener + GoodReader in side-by-side mode. I read the text in GoodReader and make notes in Scrivener (Scrivener can also show both the PDF and the notes side-by-side which I've also done).
Just reading, my Kindle Fire 8 works very well for this and is more comfortable to hold than the iPad Pro over an extended period.