From around 1994, I wrote down in a notebook the title, date finished and a quick rating of what I thought of the book. Starting in 2007 until now I use
digital journal, which basically keeps track of the same information.
I keep journals of what I've read for myself and because my daughters share my love of reading. They'll eventually inherit my library of books and I hope that one day they and maybe their children will also be interested in reading my journals along with the books.