I finally finished reading the Coffee Prince novel. I found a great blog with the english translation here. Han Kyul and En Chan were definitely different in the novel, almost more two dimensional. Since the writer of the novel also worked on the Kdrama script, it is interesting to see how she expanded and changed some characteristics for both.
Han Kyul definitely struggled with his feelings more in the drama than in the novel. He was almost nonchalantly accepted his attraction to En Chan. There's even some background info on Han Kyul's explosure to homosexuality with references to his gay American friend, Dick. That was amusing. Han Kyul drama-version had experiences with women in America, no mention of men from what I recall.
I think all Coffee Prince fans should read the novel. It's fun to see how the author originally envisioned Han Kyul and En Chan and I can appreciate how she changed things around to adapt to live-action.