From the back cover:
Six historical heroes: Doc Holiday, Nostradamus, Bruce Lee, Harald Hardraada, Owen Glendower, and Cyrano de Bergerac have been gathered together out of the mists of time. Their mission is to find and wake King Arthur, for it is time that he again don the mantle of kingship.
All you need to play The Future King is this adventure booklet and a common pair of dice. It is not necessary to first learn some seperate rules system -- nor do you need any of the odd-shaped dice used in so many role-playing games. So just take The Future King home, read it, and you'll be ready to play.