The book is a strip of paper in front of a tombstone that is beside a dead end doorway in a cylinderical forest(?) on land. To reach this area, first you have to leave the the land area and go to the sea. Once at the in the sea, Find the the large empty island. then go to middle portion of the southern most area of the island and head south. You should come across a flag surrounded with three tiny islands. Interact with the flag and it taks you to where you want to go.