I wasn't sure what I was getting myself into when I started this series. All I knew was that Miyano Mamoru was a main character and I'm a sheep when it comes to him and I fell in love with the opening. The more I watched, the more I was engrossed in the world of Durarara.
It starts out slow paced with introducing the setting and main playing characters. With each episode it got more and more interesting, even though the plot wasn't very strong, at least not to the First Viewing eye. In that way it reminds me of Baccano with how its storylines meet at a point and seems confusing until you watch it a second time and make the connections. The second half of the series, however, has a constant plot and its own arc.
It leads many elements of mystery and thriller. The characters all have twisted quirks about them and it keeps you interested in events to come.
I'm sad to see this quirky gem end, but it left enough open that there could very well be a second season. And with the Lite Novels still in publications, there's the strong chance.