The Book of 'h.a.m' is used during the Zogre Flesh Eaters quest. It is found in the wardrobe in Sithik Ints' room.
When used on Sithik Ints, he asks if the player has fought for their life against the odd monster or two. In response to the player accusing him of hating monsters and ogres in particular, he challenges the player to back it up with facts.
When used on Zavistic Rarve, it persuades him that Sithik Ints might have had motive to destroy Jiggig. In combination with other evidence, it leads Zavistic to help the player catch Sithik. This means that Sithik Ints is part of the Humans Against Monsters group.
You read this book for a while, it seems to be some sort of political manifesto about how the king doesn't do enough to safeguard the citizens of the realm from the monsters that still thrive within the borders. It sends out a rallying to all people who would want to stop monsters, to join the HAM movement.