Vertigris
I haven't read/watched past the eclipse, but apparently what follows is disappointing (according to a friend of mine who did read further). The whole tone and direction of the series changes, perhaps to expand its target demographic. I can only reiterate what others in the thread have said: Watch the movies to gain a new perspective on the story. However, the CG is kind of awkward, despite the high budget and general exceptional quality.
...But the movies are definitely a cut above the original anime.
I disagree with your friend on that one: the rest of the story is equally good imo, you can see the world expand further and there's a lot of characters development and important storyline that the anime skipped. People who decide not to read manga are definitely missing out a lot. About the tone of the series changing, yes, it does introduce magic and it becomes more of a fantastic setting compared to the earlier chapters, but it's still a dark fantasy and will always be. My only complaint are the slow updates, waiting for a new chapter to come out each month can be such a pain.
Now to answer the OP's question, just read the manga.
wink I've heard many mixed opinions on the movies, but they're still worth watching and apparently are going to continue adapting the manga till the end.