When scrolling through my list of books or looking at a book page, it's impossible to tell at a glance whether I've left any written notes about the book, either as a public review or a private journal. In general, I can't find a way to see which books I've reviewed.
It would be nice to have a visual indicator that there are some notes about the book hidden in the menus. (I imagine something like the librarian notes icon, for reference)