The Lightning Thief meets The Sea of Trolls in this well-executed, if rather plodding children’s debut by the author of the adult novel, Chocolat. In a world where the intolerant “Order” has deemed the old Norse myths as blasphemous, village misfit Maddy Smith discovers she is the daughter of the Norse god Thor. Guided by Loki and advised by Odin, Maddy travels to the “World Below” to try and thwart the prophesied war between the old gods and the new. The heroes win the day, but at least one villain escapes, hinting at a sequel. Unfortunately, Harris’s determination to include just about every Norse god in her narrative brings Maddy’s quest to a standstill at times. Some youngsters not well-versed in Odin’s family tree may find the discussion of the gods’ past grudges confusing, while others will be inspired to dig out their old copy of D’Aulaires’ Norse Gods and Giants to refresh their memories of the Vanir and Aesir. A mini-course in Norse mythology for the tween set. (Fiction. 10-14)