The Giving Tree by Shel Silverstein, seems to be a favorite amongst the adults. This may have been the first of the ten that "sold".
For $1000, there will be a dedication plaque near the tree. I think 6 sold before school was out.
This one was a lot of fun to do. It comes from the book Stars. Even though we can't totally black out the library, because of the emergency lights, we added some glow paint for when the lights are turned down.