I cannot recommend enough that anyone who likes this series should read the novel, and honestly just read it from the beginning. There are a lot of small things left out that really add to several characters even in the material that has been adapted. Haeil's internal monologue is a lot more interesting and Hee Woo also has a lot more characterization in the novel in earlier scenes to give him a bit more to him.
I cannot recommend enough that anyone who likes this series should read the novel, and honestly just read it from the beginning. There are a lot of small things left out that really add to several characters even in the material that has been adapted. Haeil's internal monologue is a lot more interesting and Hee Woo also has a lot more characterization in the novel in earlier scenes to give him a bit more to him.