Based on four novels by Philip Reeve, the screen adaptation is directed by Peter "Lotr" Jackson and stars Hugo Weaving and Hera Hilmar.
Cliffs Notes version of concept: post-apocalyptic steampunk future, cities have turned into giant roving machines including the city of London, that prey on each other for resources. So a Borg cube on wheels, basically, or a larger version of Jawas' sandcrawler. (Even the wikipedia entry for this book is a trip).
The trailer, I should note, gives away a pretty absurd chunk of the plot. Hugo Weaving'ss character Thaddeus Valentine already looks a lot like Kenneth Branagh as Dr. Arliss Loveless in "Wild Wild West," as if the film already did not look like an upgraded version of "Wild Wild West."