Livey's younger brother Darby, a math genius, brings his imaginary friend to life through a mathematical proof. Lewis's latest novel brings horror and math together in an unforgettable story that will forever change the way kids look at math equations.

Monster's Proof 2010, Simon & Schuster Books for Young Readers, New York

ISBN-13: 9781416935926

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Monster's Proof 2009, Simon & Schuster Books for Young Readers, New York, NY

ISBN-13: 9781416935919

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