More cautionary parable than intellectual jaunt, this Faustian quest novel is ultimately as troubling as it is clever. The Petros of the title had been, for much of the younger life of the narrator, a benign chess playing and gardening uncle, as well as black sheep. While his brothers, including the narrator's father, took their place in the family business, Petros, the first-born, pursued his interest in maths. The now old, disgraced bachelor appears to have done little to warrant the dislike of his siblings. The narrator's interest in him intensifies. The heart of the book and the Uncle Petros mystery lies in the reference to Goldbach's Conjecture, a mathematical theory based on the hypothesis that every even number greater than two is the sum of two primes. Devised by the great German mathematician, Christian Goldbach (1690-1764) who gave it its name, it has yet to be proved - churchyards are littered with the bones of men exasperated by it. When the narrator also decides to devote his life to maths, Uncle Petros is not encouraging and sets him a problem to solve. Should he fail, he has no right to make maths his life. It is a brutal test. The boy fails, yet refuses to give up. A brilliant celebration of the ruthless beauty of mathematics, Doxiadis's atmospheric, ingenious yarn is also an agonisingly astute study of character.