I just knew it's Sabine's video (I watched it last night) when I saw the name R. P. Kerr. I love her video too, though so far the only thing that I've learned from it is how to properly pronounce the word Einstein :DDDD
Also, I'm just starting the book but I love the authors youtube videos and it seems germane, a brief history of black holes by dr becky smethurst seems to have decent reviews and her videos are great. Maybe check her out on youtube if you're more experienced but I'm finding her book fun as a layman
I just this week finished Dr. Smethurst's book. It was good stuff, but it does focus more on a black hole's interactions with its surrounding galaxy -- presumably because that's her specialization -- rather than things like firewalls and "is there a singularity."