This is more than kind of amazing - really astounding, but... almost impossible to describe. I read it in a mad almost hallucinatory dash and may still be in a daze. Here's the publisher's blurb:
Jay Lake's first trade novel is an astounding work of creation. Lake has envisioned a clockwork solar system, where the planets move in a vast system of gears around the lamp of the Sun. It is a universe where the hand of the Creator is visible to anyone who simply looks up into the sky, and sees the track of the heavens, the wheels of the Moon, and the great Equatorial gears of the Earth itself.
Mainspring is the story of a young clockmaker's apprentice, who is visited by the Archangel Gabriel. He is told that he must take the Key Perilous and rewind the Mainspring of the Earth. It is running down, and disaster to the planet will ensue if it's not rewound. From innocence and ignorance to power and self-knowledge, the young man will make the long and perilous journey to the South Polar Axis, to fulfill the commandment of his God.
It's a bit (maybe more than a BIT) of fantasy, a lot of SF alternate history, a whole bunch of philosophy and speculation, all wrapped around a boy's coming-of-age story. It has a lot of steampunk appeal ... though it isn't your average steampunk lets-replace-the-microcircuits-with-gears story. On top of that, it has non-stop action as poor Hethor is bopped from one problem and woe to the next. Part of me would like to see this as a movie - but most of me is afraid there is no way to measure up with the vast ideas and images that Lake conjures up in a universe where the equator is a gigantic gear that separates north from south.
Even at its most fanastic and fantasmagoric, there is still a lot of hard SF in this - with plenty of details - for example of the hydrogen airships that ply this world that REALLY runs on gears.