I personally liked War Crimes: The Legacy of Nuremberg, which went into detail with numerous authors on the trials. I only read Jörg Friedrich's take on the denazification process, but it was very interesting, and I'd recommend it. This book goes along with a 12-hour documentary on the trials...at the very least, it's a great place to start to understand the changes the Nuremberg Trials brought on.

These are some good starting points that I have utilised in my thesis. In the House of the Hangman, Exorcising Hitler, The Denazification of Germany, and The End of the Third Reich

A quick google search found this interesting article (from the abstract it looks interesting at least).

At a guess, you're likely to find the least information about security services, as these were dis-established and security was the responsibility of the occupation forces. German security services were only re-established as part of the GDR and the emergence of the Bundeswehr in the mid 1950s.