THE PARROT’S THEOREM

A bestseller in France (where the author teaches history of science), Guedj’s first fiction is a charmer indeed—a history of mathematics offered up pretty as you please via a handful of likable characters, a mystery—and a talking parrot.

At 84 and wheelchair-bound, though nimble in every other way, the kindly Mr. Ruche owns a bookshop in Montmartre, where he lives celibately with Perrette, 44 years his junior, and her three children, the twins Jonathan and Lea and adoptive 12-year-old Max, who is deaf. This is the little family that pulls together with bonds of friendship and love when two things happen: Max saves a parrot from two thugs at a flea market, and Mr. Ruche receives the best private collection of math books in the world, sent from South America by his old college friend Elgar Grosrouvre. Grosrouvre is also 84 but, unlike Mr. Ruche, is facing a catastrophe. For years, he’s devoted himself to math, and now he’s proved not only Fermat’s Last Theorem but also Goldbach’s conjecture. Equally astonishing, he hasn’t published: instead, he’s confided his breakthrough work only to “a loyal friend,” partly to keep the theorems from an unnamed enemy—who, next thing Mr. Ruche hears, has apparently burned down Grosrouvre’s house and the old man with it. How to find out who it was? What to do? Oblique clues in Grosrouvre’s books and letters suggest a trail of meaning, but to make sense of them would mean studying mathematics from Pythagoras on through Fermat—which is just what the little family does, offering readers, howsoever math-impaired they be, a great introductory ride all the way from Thales measuring the Pyramids through the discovery of zero and Archimedes repelling the Romans at Syracuse. Will the mystery be solved? Well, you won’t find out about it here.

A wonderful little book, cartoonlike, yes, but tender and impassioned—and with a tour of math just as useful for YAs as for Methuselah.