After the Varrock Museum minigame a copy is displayed in case 3 on the third floor. Return text: Do you want to send this book back to the Varrock Palace Library? You can also get this book from your house's bookshelf. It is titled the History of the Dagon'hai. After completing the quest What Lies Below you can take this book to Historian Minas on the first floor (up once on stairs) of the Varrock Museum to receive 5 kudos.