I really like having both for technical and academic books. The reading experience is much better with the paper text: no glare, bookmarks on your own terms, it doesn’t monopolize my computer/other device, and other reasons. However, having a pdf is also really useful. It is easier to take my reference material to the coffee shop. Searching – indices almost always miss the thing that you want to find.
I really wish this was more common. Most of the paper+pdf combos I have are a result of knowing the author (or one of their students) and just asking them for it.
