If doomed to repeat one’s life over and over again during the 1940s, who wouldn’t try to kill Hitler? Yet not interfering with history is one of the cardinal rules of the Cronus Club, a select group of people known as the kalachakra , who loop through time in “ The First Fifteen Lives of Harry August ,” by Claire North (Redhook, $25).Anyone who breaks the rules gets punished by the club to make sure the offense isn’t repeated in the next life.