I finished watching the first season of "Vampire Knight" a little over a week ago. I think that the series is a nice companion to the manga, but it is definitely not a substitute. The anime follows the manga pretty faithfully -- a few things are omitted or the order in which they come in the story has changed, but it's nothing too upsetting. The anime also has more slapstick humor than the manga. Sometimes that annoyed me because I feel the story is at it's best when it is dark. So what's keeping me from strongly recommending this anime? Well, the anime lacks the "loveliness" of the manga. The characters are drawn sorta like those in the manga, but they lack the curly-flair and the detail of Hino's drawings. Hino draws very appealing looking males and the animators just don't have that talent. I realize that it would be very expensive to recreate the details of Hino's drawings, still, in that sense, I feel the anime is a bit soulless. One of the strongest moments in the manga is the scene in which Zero bites Kaname. In the manga, the build up to the event is violent, tense, and intense and the spread devoted to the bite was red-hot in all it's glory. The drawing is, well, "lovely" and over-the-top. The anime took a different approach and I think, in comparison to the manga, the scene fell flat.
I was hoping for a little variation in the story from the manga. From reading the forums, basically fans fall into the Kaname camp or the Zero camp. I am, of course, in the Kaname because I like bratty slightly evil characters and emo-characters like Zero cheese me off. I was hoping that in the anime, Zero would be less emo and more fierce. Rather, they've made him powerless and pitiful. Kaname is robotic in the anime. I imagine him to be seething under a calm exterior -- one of those guys with a beautifully biting tone. (forgive the bad pun) Oh well ...
As a good companion to the manga, I give the first season of the"Vampire Knight" anime 3/5. I highly recommend the manga, though, for its lovely drawings and dark and detailed story. The story comes on slowly but when a secret is revealed, it sheds light on all the past events and, for me, I felt the impact of the build-up greatly in retrospect. It's like magic. When it happened I would go back and reread the previous chapters and marvel at the little cues Hino left. The subtlety is amazing in when read in retrospect.