From the back of the book:
Prince Valient: The Storytelling Game is an exciting multi-player game in which you act out the part of a character in the lawless, romantic medieval world of KING ARTHUR and PRINCE VALIANT.
The game is social and cooperative, not competitive like poker or chess. So the rules are short and simple (about the length of a magazine article). The players take turns as the STORYTELLER: the group leader/moderator. Most of this book is not rules but suggestions, pictures, and stories, all designed to make the Storyteller's job easy and fun. The Storyteller awards FAME POINTS to the players based on their performances. Fighting dragons, solving mysteries, courting damsels; anything can gain you fame.
So if you like acting out a part, and you like to see your character become more famous as you play, you'll like Prince Valiant, the Storytelling Game!