At first glance, it's a biography of Bertand Russell. More importantly, it's a discussion of the underpinnings of logic, and the problems of finding a firm place to stand in mathematics. The humanity of the men involved in this is brought to the fore; it's not just that they're looking for logic, but they're looking away from the messy humanity surrounding them, and their own irrational brains. More than one of them goes insane, or suffers at the hands of his obsession.

It's an excellent book, if a sad one. The first and second World Wars are in the background, and the book starts with people trying to use mathematics in the service of pacifism -- ultimately, the wisdom of these men is not defining everything with mathematics, but in understanding what mathematics cannot define, and why.