"A book lying idle on a shelf is wasted ammunition. Like money, books must be kept in constant circulation. Lend and borrow to the maximum--of both books and money! But especially books, for books represent infinitely more than money."
That would make them a Bookcrossing Zone. If they would be interested in becoming an OBCZ (official Bookcrossing zone) there are a lot of threads discussing that on the OBCZ Manager thread: http://www.bookcrossing.com/---/27