The multiple worlds that Adam Christopher has created for this book are genuinely unique and interesting places in which all manner of exciting tales could be told, but unfortunately this book is not one of them.
Three quarters of the book are taken up with clumsy exposition about the setting - pages and pages of characters literally explaining to the central character how the multiple worlds work - and the remaining quarter is filled with confusing and nonsensical action. The central character is supposed to be a private detective who is the key to an inter-dimensional plot, but he never does any detective work, and just gets dragged dumbly along, never doing anything to advance a story that in truth could have carried on quite well with out him.
The conclusion is supposed to be an exciting series of crosses and double crosses, but none of the characters' behaviour makes any sense, the betrayals being present more because the author felt they were required of the genre rather than because they had anything to do with the motives on the characters. I kept expecting a clever twist at the end that would suddenly make the rest of the book make sense, but when in came to the final page I was just left disappointed.
Ultimately Empire State is an ambitious attempt to cross multiple genres, but sadly it fails to satisfy in any of them. Disappointing.
(Also - why is the main character so obsessed with his hat?)