I imagine most GMs have a modest collection, some that they review occasionally, to study an endgame that they lost recently or for good calculation exercises, and some that they read once and leave on their shelf. Those who love books and chess history will probably have a lot. I suspect books are still valuable just because writers usually invest more time than they would on a video and they have editorial checks which improve them, but that's changing rapidly, especially on Chessable, and it's probably already the case that you don't need books at all. I'm not really sure honestly.
A few years ago there were some great Chessbase India videos about IM Saravanan's book collection and as a fellow book lover it was fun to listen to him talk about which ones he loved and why. But I just watched this video about an incredible chess library. If you love books and chess history it's a must-watch:
www.youtube.com/watch?v=y5TS-QpRHNA&list=WL&index=91
A few years ago there were some great Chessbase India videos about IM Saravanan's book collection and as a fellow book lover it was fun to listen to him talk about which ones he loved and why. But I just watched this video about an incredible chess library. If you love books and chess history it's a must-watch:
www.youtube.com/watch?v=y5TS-QpRHNA&list=WL&index=91