One of the Japanese promos calls it "Da Vinci Code meets Jurassic Park".
I think that sums it up pretty nicely. It's got dinosaurs, spies, intrigue, action, and conspiracy, all rendered in lovely film noir-esque art with a little fan service cherry on top (Lily!).
And for the slightly geeky, it's got cool (and sometimes obscure) references to art, literature, film, history, science... you name it. Definitely a manga for adults!