Edward Snowden, a young computer genius working for America's National Security Agency, blew the whistle on the way this frighteningly powerful organisation uses new technology to spy on the entire planet.

The saga of Edward J. Snowden, the man whose leaked documents revealed the Orwellian dimensions of the National Security Agency, reads like a le Carré novel crossed with something by Kafka - at least it does in Luke Harding's new book, The Snowden Files ... But the book still gives readers, who have not been following the Snowden story closely, a succinct overview of the momentous events of the past year. And if it leans toward dramatizing everything in thrillerlike terms, the book also manages to leave readers with an acute understanding of the serious issues involved: the N.S.A.'s surveillance activities and voluminous collection of data, and the consequences that this sifting of bigger and bigger haystacks for tiny needles has had on the public and its right to privacy.