Mark Buchanan in New Scientist:
Good stories need rich characters that we care about, not mathematical theorems, however fascinating. So a work of fiction subtitled A mathematical novel makes you fear that it may only expose the tremendous difficulty of blending science and logic with the emotion and dramatic tension required of good literature. Fortunately, in this case that fear is misplaced, because A Certain Ambiguity succeeds both as a compelling novel and as an intellectual tour through some startling mathematical ideas.
Just before his death, Indian mathematician Vijay Sanhi entices his grandson, Ravi, into the world of numbers via one of its mysteries. Punch any three digits into your calculator, he tells Ravi. Then punch in the same three again. No matter which digits you choose, he claims, the resulting six-digit number will be exactly divisible by 13, that result divisible by 11, and the last result by 7. You will always end up with the same three-digit number you started out with. Amazed to find this is true, Ravi soon works out why (a clue: 13 × 11 × 7 = 1001), and falls in love with mathematics.