In your dreams, a mysterious talking beetle confronts you with vexing mathematical queries. Do you ignore it and wake up, convinced that not even sleep provides respite from your algebra homework, or plunge into a bizarre adventure filled with more strange questions?
Robert, protagonist of “The Number Devil,” is a 12-year-old boy who faces this choice and opts to follow his curiosity through a world of math despite not enjoying the subject at school. Written by Hans Magnus Enzensberger and illustrated by Rotraut Susanne Berner, “The Number Devil” follows Robert throughout his imaginary adventures as he explores fields ranging from number theory and geometry to combinatorics and logic.
“The Number Devil” is structured as a series of 12 nights, each covering a different and increasingly complex topic. Fractions give way to fractals as Enzensberger and Berner use vivid imagery to make abstract concepts intuitively understandable.
Robert quickly learns that the aforementioned beetle is the titular number devil and gradually comes to appreciate his new teacher. The devil’s teaching methods appear highly unconventional, and Robert is initially hesitant to embrace them, but he soon comes to enjoy his nightly lessons.
Endless chains of numbers hooked to the devil’s walking stick represent repeated decimals, while infinite rabbit families illustrate the growth of Fibonacci numbers. Enzensberger captures the sheer wonder experienced by students forming connections between seemingly unrelated fields in his fantastical depiction of seemingly unintuitive ideas, allowing me to experience the joy of figuring something out for the first time all over again.
By abandoning standard notation for more imaginative terminology — square roots are rutabagas, factorials are vroom numbers, primes are prima donnas and irrational numbers are unreasonable numbers — he separates math from any preconceived notions of complexity. Reading “The Number Devil” didn’t teach me how to solve differential equations or find 2D convex hulls, but it did help me appreciate math as more than an academic subject.
On the final night, Robert learns that the number nevil’s real name is Teplotaxl and is invited to Number Heaven. After reaching the entrance, Robert worries that he’s misplaced his invitation and may not be allowed in, to which the number devil responds: “Don’t worry. Anyone who really wants to can enter. The trick is to get here in the first place. And that, as you can imagine, very few manage.”
Mathematical thinking represents a way of approaching problems just as much as it is knowledge of how to solve them. What I’ve learned about geometry might not directly apply to a proof in game theory but could help me appreciate a common theme or idea. My own experiences with math have taught me to seek out the unexpected connections between vastly different fields, and developing a desire to explore beyond textbooks has helped me enjoy math for its own sake.
As Robert learns, the biggest factor distinguishing mathematical titans like Pythagoras from students struggling with geometry is simply an interest in learning more. Curiosity isn’t a substitute for understanding, but knowledge without passion can never become insight.
Although the number devil is unable to guide Robert along his journey any further, devastating both, Robert’s newfound love of math enables him to thrive in a class he previously detested. His independent derivation of Gauss’s formula for triangular numbers shocks his teacher, and Robert “silently thank[s] the number devil” for teaching him how to approach and appreciate mathematics.
I’ve always enjoyed learning about the beautiful patterns found in math, but reading “The Number Devil” helped me appreciate why mysterious patterns have enamored humans for thousands of years. Math becomes magic through Enzensberger’s writing, and I find “The Number Devil” utterly captivating; each time I return, something new puzzles and delights me. “The Number Devil” is no ordinary series of math lessons, and any student can learn from both Enzensberger’s delightful prose and Robert’s approach to learning.
Rating: 5/5





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