What is the name of this called - leaving books for others?

Question

Let says that I had a book, wrote my name and location in it, left it in a public place, and asked the person who picked it up next to do the same....
What is that called? I would like to find out more about it on the net
Thanks

Answer 1

I've called it booksharing. This website calls it bookcrossing.
http://www.bookcrossing.com/home

Answer 2

A chain book. It passes from hand to hand or name to name and notes are taken carefully in the margins.