I don't know how I missed this drama but I'm glad that I watched it.
Prison Playbook is an awesome drama with its well-written story and amazing cast.
The lead actors stole my heart!
Park Hae Soo portrayed Kim Je Hyuk perfectly. He seemed dumb most of the time but he had his moments of nasty temper. He survived prison with his dumb wit, and fame and it was superb!!
Jung Kyung Ho as Lee Joon Ho, is a dream guy for every girl just like Je He says. (My new crush!) He is really the best friend one would hope for. The way he handle every mishap in Kim Je Hyuk's life and take care of every one else makes you swoon over him.
Now all the other support roles who still played a significant role in the drama like Krystal, Min Chul, KAIST (superb acting of lisp), Dr. Ko, Loony (amazing display of character btw), Captain Yoo (handsome as ever), Lieutenant Song, Lieutenant Paeng and Jailbird!!! Jailbird was awesome!!

I would definitely advise you to watch this drama! It deserves 10/10!!