In God's Underground, by Richard Wurmbrand, is a 268 page book telling the stories of how Richard Wurmbrand ministered in prison to other prisoners.
The Torchlighters: The Richard Wurmbrand Story
All the Paths of the Lord are Mercy and Truth
Share Their Voice: Shafia's Story
The Torchlighters: The Robert Jermain Thomas Story
I Found God in Soviet Russia
Underground Saints