This is one of my favorite parts of my classroom library! At the beginning of every year after I introduce the classroom library and we go over all the rules, I also show my students how to leave a short review about the book they just read. I want them to evaluate the book in a short but honest way. They leave a review only when they have read the entire book.
Students use a post note to write their review on and leave it in the book's inside cover for the next classmate to find. Students enjoy reading the reviews and it lets me know which series and authors are most popular.
I print this in color, frame it, and leave it in my library all year long.