This story (part 3 of 4 in Jason Aaron's magnificent run) is one of the most chillingly introspective bits of literature you will ever read, as Frank Castle finds himself incarcerated in Ryker's Island after the events of the previous volume (PunisherMAX: Bullseye). Locked up in the most dangerous environment he can find himself, Castle is left to recover from the previous brutality with nothing but his own thoughts and guilt to keep him company - left to ponder whether it is all worth it and struggling to understand his Punisher persona.
This all unfolds with the threat of a prison-wide riot looming menacingly in the background and we're left to wonder how a mentally and physically destroyed Punisher is going to get out of this predicament.
The story is ultimately an exploration of Castle's family-life in the aftermath of the events told in Born and the metaphorical prison he found himself in in trying to adjust to civilian life again after the utter violence and brutality of the war - this exploration turns him (somewhat) into an unsympathetic character and one begging for redemption.
Forget the 70s romanticism of 'a mob hit gone wrong' being the origin of the Punisher - Born and Frank tell the real story and it is one that is a lot more poetic, heartbreaking, and hard to swallow.