Ever watched a wildlife program where animals are tagged and released into the wild so researchers can follow what happens to them?
Well these people tag and release books and track their travels through entries on this website.
The finder is asked to go to this website and register the find and then to register the time and place of release for others to find.
If your parents are readers, point it out to them, because this was not set up for students, it was set up for everyone.
If this seems fun, you should talk it over with your parents. It is fun, but it is also net based, and the usual Internet safety rules apply.
(who has finished reading Tamora Pierce's Trickster's Queen (its a great read for 7-10 fantasy lovers) and has started Neil Gaiman's Smoke and mirrors (Short stories and definitely a bit strange).