Ask HN: What's the best device for reading technical books?

Lately I have been reading many technical books — e.g. O'Reilly — and am looking for a better e-reader experience.

Right now I read either on my MBP, which has the advantage of large screen real estate, or my iPhone, which is portable. Both have high-DPI screens so the text is crisp. I had a Kindle Paperwhite (now dead) that was much, much better for eyestrain.

So what's a good compromise between these? Ideally an e-ink tablet with high DPI for text and illustrations?