Two sisters solve a series of math problems and logic puzzles to make their way through a magical realm.
In this middle-grade novel, Mohr (Classic Poetry for Your Little Genius, 2014) draws on the works of Lewis Carroll to tell a story that uses a quest to connect a series of math problems. Twin sisters Lulu and Elizabeth are drawn into the journey when Lulu, the younger and more excitable sibling, loses her favorite silver glitter gel pen to a magical magpie. She convinces Elizabeth, who would prefer to stay home with her books, to help her recover it. The two discover an enchanted book that presents challenges in rhyme and provides a new clue after the girls solve each puzzle. They work with tangrams, calculate heights, find the midpoint of a circle, move untrustworthy creatures across a river, and learn about exponential growth in order to reach their destination, assisted by a talking pig, a wolf named Manxome McLay, and a group of Slithy Toves. Callout boxes invite the reader to solve each puzzle along with Lulu and Elizabeth, and each chapter concludes with a series of additional problems related to the concept discussed. (Answers are provided in an appendix.) While Lulu and Elizabeth have clearly defined personalities, they are also preternaturally earnest (“you keep trudging through to get to that gratifying state of Q.E.D.”), and both character and plot take a back seat to the narrative’s primary purpose of providing a context for the math and logic questions. Although Mohr displays a strong grasp of math and Carroll, minor errors in the text (“Ex Caliber” for King Arthur’s sword; “limerick” for a poem with four lines and a non-limerick rhyme scheme) detract slightly from the otherwise strong presentation of classic mathematical theories in terms young readers can easily follow. The book is a useful educational tool, though not a novel many would choose to read for pleasure.
A helpful series of classroom exercises, connected by a story about twins exploring a hidden world.