Durarara starts when a high school freshman Mikado Ryuugamine, who always wanted to live an exciting life, transfers to a highschool in Tokyo at the invitation of his best childhood friend Kida Masaomi. While Kida is showing him Ikebukuro, they witness the "Black Rider", an urban legend that is supposedly headless rider of a black motorcycle. And so the story starts and we get introduced with a lot of interesting characters and interesting plotlines.
From this description it may seem that Mikado is the main character but the truth is, show has no leads or actual main characters, just bunch of characters who are all interesting in their own ways.
Light novels were adapted into successful anime, which I think was one of the best selling anime in Winter-Spring season of 2010. There are 9 volumes of Durarara (shortened DRRR) light novels out, and anime adapts the first three.
If you have watched anime and you are interested what happens after, you can check out http://anni-fiesta.livejournal.com/, for light novel translations.
Now here is some nice fan art, mostly from pixiv.
Now here is some nice fan art, mostly from pixiv.