Guilty Crown opens up with a beautiful song that sets the mood for the anime. The anime is mostly action and a theme set on taking down those behind a vrius outbreak that took place 10 years before the present anime known as "Lost Christmas."
The anime focuses mostly on Shu Ouma, who acquires the ability (by accident) to extract peoples' voids and use them as weapons, and Inori Yuzuriha, a singer (she can be seen singing in the opening). To make a long story short (not much of a spoiler here, anyone can guess) Shu and Inori end up having a fated encounter that eventually leads to him gaining his powers and joining a terrorist group known as the Funeral Parlor.
It has mostly everything. A story line that doesn't bore with twists and turns along the way, a romance (though it simmers slowly throughout the anime), and tons of action. Visually, it's stunning. I've never seen an anime that flowed so easily throughout the action scenes as this one (and that's hard for me to say because it takes a lot to impress me).
The anime flows very easily (story wise) with enough villians and character backstory that isn't spread out so it's hard to remember. It's one of the best anime I have watched in the fall '11/winter season and I'm shocked more people have not watched it. I would recommend it to anyone.