Demonic tome

Also titled The Confession of Ellemar.

This book is found during the Shadow of the Storm quest. It's the final confession of a Saradomin mage who, while studying some of the dark arts, accidentally summoned a powerful demon from another realm. One of the most important uses of it is that it has a chant in it that is needed during the quest.

After the quest, this book can be found on the shelves in your house.