Being a fan of spy-novels (Tom Clancy-style) and movies, watching the movie "Breach" which is based upon the story of Robert Hanssen's unmasking immediately fascinated me. So I read this book shortly afterwards and discovered that the thing you'd normally account to spy-novels happened (and probably are happening) in the real world as well, and that the downfall of the Soviet empire has not put and end to this. Also this book gives a unique opportunity to get a grip of the personality of a spy of Hanssen's magnitude, as we not only get to read the opinions of colleagues and psychologist, but also Hanssen's very own mails, E-mails and web-postings. I read this book on two subsequent days, which is a clear sign that although (or because?) it describes real people and events, it is even more thrilling than many novels I've read. People who watched the movie should also consider reading it, since Chris Cooper gives a Hanssen a much more charming (and obviously less detailed) appearance.