The script is well written and is enjoyable if you know a little about gambling and cards. Unfortunately idk nothing about both so it was hard for me to keep up with the story from the beginning.
The main drawback of this drama is that there are so many supporting characters, so it's hard to figure out who is who for a long time. It took me several episodes to differentiate the various roles of the characters because there are too many to keep up with.
The first eight episodes or so were uneventful, mainly focusing on how Yo Han tries to adapt to life in prison, but things start getting interesting when the action scenes come into play, around the second half of the drama.
The plus point is that all the many supporting characters are also veteran actors, which is like an extra cherry on top of the flawless plot. So obviously the acting is top-notch.