"This engaging short book is both a mathematician's reflections on grief and a mathematically-informed theory of grieving. Michael Frame retired in 2016 as a professor of mathematics at Yale University, where students fought for a place in his course on fractal geometry. Students appreciated his use of accessible examples- decalcomania paintings and illustrations of cats to explain mathematical concepts-and stories of his work and friendship with the founder of fractal geometry, Benoit Mandelbrot. In this book, he continues his work to make mathematics accessible, using his experiences with grief to give uninitiated readers insights into advanced topics in geometry. The inability to repeat an "aha moment", when you first learn something, is one type of grief that Frame examines. He connects this irreversible loss of perspective to more consequential grief-loss of a career or of a loved one-and explains ways he has thought mathematically about grieving and coping with grief. Frame is an authentic and sympathetic voice. He retired after discovering that he had an inoperable brain tumor and feeling the effects of his cancer on his teaching career. His connections and insights make this a timely and moving book in our time of personal and collective grief"--