KNK is undoubtedly a tough work to get into. The story is labyrinthine and the order is intentionally jumbled. The concepts that recur with greater clarity in later Nasuverse works are getting a test drive here, and it does show. You will be confused, you will be annoyed, and you will probably need to read slowly.
This being noted, KNK is a really good story for a certain audience. I would restrict it to people who've played Tsukihime (ew not the anime, I mean the actual VN) because a lot of the concepts and themes recur between the two stories. KNK, being a written novel and not a VN, explores them in even more intense detail so you will need to read between the lines, but at least you won't be lost and floundering. Expect a ton of exposition and complicated explanations that all have significance and meaning.
If you are among those people, I think the story will be very enjoyable, especially because KNK is a big part of the history of the Nasuverse. There have been complaints about cokesakto's translation being too fluffy and expanding too much upon the original work, but regardless it reads well. It has its share of comedy, but it's generally somewhere between action, mystery and thriller; the plot seems to be a bit episodic but everything does come together. Mirai Fukuin is also recommended.
I read the novels in the order in which they were presented, not their chronological order, and I think if you have enough perception to follow along, you will understand what is going on. You might have to read over a few parts multiple times and keep your eyes peeled for hints as to the chronological order of events, but by reading the novels in their original order, you can capture the full extent of the storytelling.
I watched the movies as well and I thought they were really fun, but they suffer from the nature of their medium. Kn K
is a story that is overflowing with background and hidden exposition. You simply cannot capture it all in the runtime of seven movies, and so you WILL miss out on a lot of the good stuff. Not as much of the movies is kickass fight scenes as some would like, either. I'd only watch them after reading the novels, in which case they're a fun followup. I thought #6 was the worst because the plot changes were most obvious there, but they were all good adaptations - just too short to capture the stories they came from.