The book was well written and new. But if it continues to stand alone and unsupported it's ongoing sales are just going to rot. WotC need to release more content (e.g. a major adventure) to encourage people to actually use the setting*, not churn out an endless stream of unsupported cookie cutter setting books and expect people to continue to buy them.
In comparison, Eberron has a huge amount of 3rd party content either out now or out soon, and the source book isn't even out yet. And Greyhawk and Planescape have more support from WotC, even though they don't have setting books yet.
*As I've said before, I haven't seen any evidence of Ravnica set campaigns, the people who have bought it cannibalise it as a splat book.