I can't stand trying to use reference books, especially with diagrams, on my Kindle. My bookshelf is full of all kinds of reference material and my favorite books.
I generally buy it for the Kindle or Audible first and if I really like the book or it was especially thought provoking and I want to be able to dig in to it again at some point I go buy the hard copy.
I do most of my reading while traveling so I rarely (maybe not even once in the last 5 years) carry anything other than my phone or Kindle for reading.
I really want a large e-reader for technical reference books. A lot of them are only available as PDFs that don't scale at all to smaller screens.
If a manufacturer made an e-ink reader with an a4-size screen with no always-on backlight (for shame, amazon!) and with physical forward/backward buttons, I'd buy it in a heartbeat.
I generally buy it for the Kindle or Audible first and if I really like the book or it was especially thought provoking and I want to be able to dig in to it again at some point I go buy the hard copy.
I do most of my reading while traveling so I rarely (maybe not even once in the last 5 years) carry anything other than my phone or Kindle for reading.