The Secret Speech by Tom Rob Smith
I really enjoyed Smith's last novel, Child 44. This sequel takes place three years later, and Leo is now in charge of a homocide department. After Khrushchev gives a secret speech, some former MGB agents start being harrassed and stalked as a result of their involvments in arrests and torture. Leo discovers that their common link is one particular prisoner whom he also has a connection to due his former work.
The novel was strongest in the first half when Leo was trying to uncover exactly what was going on. The last half is more of a series of action sequences. One of the most interesting things about the series is simply the fact that they are set in Soviet Russia, adding a whole extra layer of intricacies to the politics involved in these people's lives. With that, Smith does a good job of throwing in important events from the history of the Soviet Union and using them as the settings of his novels. There are also a few twists throughout the book that help keep the plot going forward.