Errr.. it's hard to explain what is Anima about... You can find some info here and here and also in some discussion thread on Anima board here, a review of the corebook here. And there you can find "Nightmare become true", a fan-made introductory kit with a little rules review and an adventure. (didn't read it so I don't know if it's good or not).
To sum up, I can say that Anima is a fantasy RPG, inspired by mangas and video games as Final Fantasy for example. The world is very interesting, full of plots, big ennemies, secrets and weird things. It seems to be "low fantasy", as the world's inhabitants doesn't know that some supernatural things exists, and there is the Inquisition to forbid every supernatural stuff or beings (wizards etc.). But, in reality, Gaia is a very fantasy world.
It's not really medieval-fantasy, because some places are inspired by middle-age, others by Renaissance, etc. sometimes it can even reach Industrial Revolution for scientific level.
The rules are very good (in my opinion ^^), because you can customize your character, build it as you want, very freely. They use a d100, and a combat chart (quite as in Rolemaster, but Anima rules are very, very lighter than Rolemaster). They are 4 types of supernatural powers : psionic, magic, summoning and Ki (very visual combat technics, you can custom build it for your character).
For GM, in Anima you can play every gaming style : epic fighting, dark intrigues, worldwide political plots, even dungeon crawling or Indiana Jones exploration if you want, Cthuluh style horror game, whatever game style you like, you can do it.
If you got bore of Archwizards, orcs and gobelins, drows and dungeons, Anima is made for you, because it will change you gaming horizons a lot. Gaia is a fresher world, with only humans and a very interesting setting, a new way to consider fantasy RPG.
So, I hope you'll like it And sorry, there's no official campain (and there's no planned in the future, only an adventure compendium, in longer term future). With the GM screen (out in France and Spain, next release in english I think), there's a booklet with new rules, 20 pregen characters and a very very good official adventure.
PS : If you can read french or spanish, there's a lot a things I can give you to discover Anima.