In the classic tale The Pied Piper of Hamelin a mysterious stranger lures both rats and children from a small German town in 1284 with his beautiful hypnotic, music. In Moon Song , a new, romanticized version of this legend, the piper is a handsome king who woos Leisel, a poor maiden despised and feared by the narrow-minded villagers because of her magical powers. Liesel and the king band together to free the children, who work in the mines for the evil Baron Schmidt. The plight of the children tugs at the heart strings and the romance between Leisel and her benefactor is easy to accept. This fairytale-like romance is ill served by episodes which find Leisel helping a friend, a victim of incest, ``miscarry,'' with a potion, and that have the king showing Leisel nude pictures from a deck of ``special'' cards. Certainly, the original story had a dark side, but these scenes are just incongruous within the rest of the novel. --Lydia Burruel Johnson, Mesa P.L., Ariz.