Heart of Darkness reviewed on a post-it
The idea for books reviews on a post-it note I came across here, on The Perpetual Page-Turner, Jamie's book blog. It would work great if you have a class library; if not, film reviews on post-it notes are an alternative.
Things like writing on post-it notes (and super short stories, 100-word sagas and Twitter stories) work especially well if you get the writers to collaborate and work on the writing and rewriting to squeeze as much information as possible in. They're also a lot of fun to share and award prizes to.
My example there isn't actually a post-it: I used recitethis.com and just happened to like that design more. You could use real post-its, but a digital tool is also fun, especially if that means you can share somewhere else, like on a blog or Edmodo.