It is just that good.
It is also a book that is hard to categorize. Is it SF? Is it Fantasy? Is it Romance? Is it intrigue? Is it all of the above rolled into one with great big steampunk ball? Yes, but don't let that spook you. All the elements are balanced just right.
This is the story of Taya, an icarus, or courier who uses wings made of the mysterious lighter-than-air metal, ondinium, to soar over the city of the same name. Ondinium has a rigid cast esystem, children are placed in their caste at a young age, after being evaluated by the Great Engine that is the City's heart, literaly as well as philosophically. Those with the temperament and constitution to become Icarii move freely around the city, and live outside the caste system. Taya has aspirations toward becoming a diplomat. One day she rescues a young high caste woman and her son from a terrorist bomb, and her plans for her future are forever changed. Things are not as placid in Ondinium as it would seam on the surface. Taya is thrown together with two highborn brothers, one handsome, brilliant, and charismatic politician, the other a quiet surly, but earnest, outcast. Both brothers have radical ideas about the future of the city they love. Both, might kill to see their ideas become reality.
That just scratched the surface of the storyline in this book. Pagliassoto's world-building is super. She shows us this world from unexpected angles with well rounded secondary characters ranging from an aspiring couture dress designer who's only goal is life is snaging an upper caste patron,, to elite Engine programmers dipping their fingers into radical politics. She does a fantastic job of putting the reader into the city of Ondinium, but unlike some writers she does not stop with world-building. The plot twists and turns enough to keep any reader guessing what will happen next, and the end, although not a big pink spun-sugar bow, is satisfying enough for a Romance fan looking for a HEA.
I think the strength of this book is it's straddling half a dozen genre. It is a prime example of literary hybrid vigor. Unfortunately that may also scare strict genre readers away, andit makes the book hard to market. It will probably keep the book from both the sales and the award nominations it so richly deserves. I read all the Hugo nominees for 2008, and I like several of them very well, but when it comes to texture, storytelling and originality Clockwork Heart blows them all out of the water .