Erin Hunter 
Warriors: Secrets of the Clans 

Now the truth can be revealed Look within to find:The mystical origins and secret legends of the Clans.An insiders’ tour of the Clan camps and territories.The histories and characters of each Clan, and information about their leaders and medicine cats.Knowledge of cats outside the Clans.The tenets of the warrior code.Prophecies and omens, and how they have been fulfilled.And many more truths about the secrets, beliefs, and daily lives of the cats of the Clans.