I review every book I read on this site, The Litt Review. I want to get better at thinking about books instead of just passively reading them, and writing a review is a good way to do that. I also write private notes with all of the quotes I underline and all of my marginalia, as well as all vocabulary I didn’t recognize, but I generally don’t share those publicly.
Previous to 2017, I would just write down each book in a list. You can read those, here.