This enchanted tome magically records the likeness each humanoid slain in its vicinity, preserving a snapshot of their life and memories. The book can be read to glean superficial information about it's subjects. As an action, you can tear a page from the book to summon a ghostly spirit of its subject, which will be magically compelled to answer questions. The spirit knows nothing the owner did not know in life.
The Demon Lord Elgor Ithym is said to have a keen interest in this book...
What’s a face book if not a large collection of identities being monitored?
Well, historically (and I mean in the 1990s) it was a collection of names and photographs of all the new students at your college, to help in meeting people and/or to see who's hot.