Following the intuitions of "Fate / Stay Night", Kara no Kyoukai film serie is basically a post-modernist cocktail of modern anime stereotypes: partly a school comedy/drama, partly adventure & magic show and partly psychological thriller. This is a elaborate, but unstable construction - many ingredients, but too many of them (magic elements are good example) function like a weak links. When show is more chamber-like, portraying the psychological tension between characters it can be very successful, but also too often falls in pathetic tone and self-indulgence. Lets say it: Kara no Kyoukai tries to be more than it is. Plot is rather episodic and trivial and negative characters (there was really a need to put enemies in?) uninspired. Sometimes anime takes the form of serial killer thriller, which isn't a bad thing, but using Matrix-like fight style and extreme, gore violence (a' la Elfen Lied) maybe wasn't necessary. Of course there are positives - whole protagonists cast is adorable, especially main heroine Ryougi Shiki), balancing between her alter-egos (male and female), sense of predator and growing human feelings - probably one of the most interesting female anime characters ever. Art and animation is gorgeous, as well as music. But what makes this show worth watching is unmatched, morbid, gothic-like and romantic atmosphere which additionally gives the suspense to most tragic/terrible visions.
First (but chronologically speaking rather five) implementation maybe isn't best introduction to this infernal show - it's rather simple and trivial "ghost story" (a' la Mushishi) but slow-pacing narration holds in tense and mix of urban / magic visions is already present.