Honestly it exceeded my expectations and I really liked it. What most stayed in my mind after watching it was Bryce. There's one scene in episode 4 which was top-notch cause that's when something clicks and he starts feeling this uncontrollable fury against Stephen. It will remain my favourite scene. His character both in the drama and in the webtoon is despicable and in my opinion it was very well portrayed, the acting is a 10/10. The rest of the cast was awesome and Park Jihoon was honestly a great choice as the main lead. The dude's eyes are really Something.
Regarding the action scenes, I loved how Real it looked, for example the blood was there and it wasn't exaggerated, and also the bruises/haematomas looked realistic enough. I totally LOVED that director/writers added some of Gray's tricks when fighting, like the use of the pen, the book, the curtain, etc. and his calculations and mental notes when thinking what will be his next move.
Music? I don't really remember anything special. I think I was too focused on the story that I couldn't pay attention.
Rewatch? Totally.