From publsiher blurb:
Call to Arms is a book line for players and gamemasters alike. Each book focuses on a different type of item, expanding rules for those items and adding everything from new mundane and magical examples of the item to new character options related to the item.
Call to Arms: Tomes of Power (Revised) updates one of the original Call to Arms books to the current design and includes a vast expansion to rules and magical options related to books and other written material. Discover everything from why you’d want that Heritage Book, to why you shouldn’t want (though perhaps you secretly do) to plumb the depths of the fabled Necronomicon. In addition, Tomes of Power (Revised) introduces new books, both magical and mundane, and new rules for gamemasters to provide greater exploratory challenges in foreign languages and ancient texts.