I love Angel Sanctuary... it's one of my favourite manga.
I didn't like the anime very much through........ since the anime is so short, unfortunately you've basically allready seen the entire thing. (There's only 3 OVA episodes that cover the first three manga volumes) It's been released by Central Park Media, the OVA on one DVD.
The OVA was basically made to promote the manga.
Which is a shame, since it's such an fantastic, dark and epic story spanning 20 volumes of manga. The manga is being released in English by VIZ, and they are currently up to volume 7.
I think you'll like the anime, it's short but still good, the animation is okay and the music good too, but it kind of leaves you hanging for more (of course since there's another 17 volumes of the story to go) but if you'll willing to give the manga a go, I would read it.
If you liked stories like X and other shoujo/angst/end of the world type stories, you'll like Angel Sanctuary. Plus the artwork is simply breathtaking. Kaori Yuki is a genius.
Of course, if things like incest, homosexuality and other such thing bother you then I'd probably give it a miss... but if not, go for it.