Can an intrepid toy mouse help a child venture out of his comfort zone? Marco Polo is a retired Christmas ornament, but in his mind he is a great mouse explorer. Because he's tiny and likely to be lost, he is the least-borrowed of the Book Buddies--toys that children can check out of the library just like a book--and he almost never gets to leave the library. But the little mouse finally meets the right match in Seth, a boy who is about...