Budding conspiracy theorists and mystery lovers will be intrigued by this set, which suggests plausible and more sensational (aliens, ghosts, strange natural forces) explanations for each historical mystery. Authors outline the theories and objectively present the arguments for and against each. Although the books are written at an upper-elementary reading level, they are also likely to appeal to older readers, especially reluctant ones, who will be drawn to the topics.Good choices for middle level and secondary high reluctant readers.