3: Broken Valley, Secret Passage, a book on the floor beyond the locked door Martis opens, past a spider web.
This one I'm a little confused. I have DKS xbox version. Never found a book on the floor (I could have missed it) but there is one in a chest in a room that opens when you press a hidden wall panel after freeing Martis. Sometimes this room is not accessible because of a cave-in (I don't know what activates the cave-in).
