In 2007, I started doing "Books [Year]" tables in my journal (they have their own tag), where I list author, title, the months I started/finished reading, and a very short note on what I thought of the book. Since I have a LibraryThing account, I also mark the books I'm reading with the start/finish dates. Apart from that (and the general info you can enter on LibraryThing), I don't keep any notes.