I've now read 21 Magic Tree House books to my son, and he truly has enjoyed them all. In this series, the author employs a creative time travel portal - siblings Jack and Annie visit exotic times and places through the books they discover in Morgan le Fay's enchanted tree-top bookmobile. My son particularly enjoyed following Jack and Annie on their adventures in Pompeii (featuring Hercules), outer space, under water, and the Wild West (where he learned the song Red River Valley). He's reveled at accompanying Jack and Annie when they've met pirates, ninjas, knights, mummies, and Eskimoes. Conversely, as a parent that frequently reads children's books aloud, I've often been disappointed with the books' repetition, limited vocabulary, and uninspired plot development. Fortunately, that was not the case with Mary Pope Osborne's most recent tree house installment, Civil War on Sunday. Like her other books, Osborne offers young readers an intriguing view of a complex subject, in this case the Civil War. She also introduces Clara Barton and provides some insight into the birth of the Red Cross. As is often the case, Jack and Annie learn a difficult lesson in compassion. But the Civil War on Sunday goes deeper. Rather than serving as mere interlopers in significant chains of events, here, for the first time, Osborne actually makes Jack and Annie relevant to the thread of history. (Sorry, but I can't explain how without spoiling the story.) This minor adaptation goes a long way, particularly towards keeping a young reader's attention through the closing chapter. (Even four-year-olds quickly discern that the concluding chapters in most of these books - once the Tree House returns to Frog Creek - are not very entertaining.) This is Osborne's most complete effort, and I hope she continues her series in this new direction.