It is folklore that Hippasus was drowned by Pythagorians for proving a fact that today we interpret as the irrationality of root 2. In this simple form, this often repeated myth is quite unbelievable. Michaelides' novel is a modern reformulation of the crime. The book is a well crafted piece of historical-math-fiction. However, its basic storyline is just as unbelievable as the original legend, and ultimately it resonates hollowly. The book has several other weaknesses. As a work of fiction, I found that the prose was rather flat and uninspired, though it's possible that the translation has detracted from the original. The mathematical topics that are woven into the text are reasonably well presented, but somewhat predictable; they are very much the tried and true standbys.
The main attractions of the book are its originality of concept, and the fact that considerable care has been taken with its design. The book is unusual in that it has several parallel strands, which are all presented with an historical perspective: in particular, apart from the mathematics, there is an artistic strand, built around Picasso, a fictional underworld/prostitution theme, and a depiction of a number of real political events. The integration of these strands has been well accomplished, and makes the book original and innovative. If you enjoy the fiction-math genre, it is certainly worth reading.