In a very very far future, when humanity is but one of many races who have made it to the stars, typical human hubris accidentally awakens something ancient and malevolent, and very very smart. The only escapees of the expedition are a small family of four, with two precious cargoes: a possible means to defeat the awakened, and a spaceship full of children in cold sleep, but their landing is on a pre-industrial world inhabited by pack-minded dog-creatures, deep in "the slowness", the zone of the galaxy where advanced machinery simply doesn't work.
And their only potential means of rescue? A librarian, a patchwork man put together by a higher being, and two sentient seaweed trees on go-karts.
I'm thinking I probably don't need to review this, because that insane summary either completely turned you off, or totally sold you this is a must read. Clearly I fall into the latter camp!
Personally I think this is a wonderful book, which is why I'm on my third re-read of it. The tines (the dog-packs - bonded via high frequency sound, there's no magic involved here) and the skroderiders, the cybernetic tree organisms, are some of the most fun and interesting aliens ever written, and the desperate race of the would-be rescuers to get to the tines world and potentially save the galaxy is so well done.
There's a lot more really interesting ideas too - the entire makeup of the galaxy is fabulous: deep in the center, not even sentient thought is possible, further out is the slow zone, where civilizations arise and industrialize, but at a glacially slow place, and eventually the beyond, the outer edges, where eventually the most successful races emigrate and can develop technology far beyond what is possible in the slow zone. Eventually individual ascendence into a "power" is possible, for some, yet even the most technologically advanced can't operate properly if they are forced back into the slow zone.
As for characters, there's some serious complexity. We have sleeper agents who don't know that they are, betrayers, schemers, a man who isn't sure he even is a man, a whole load of characters who are in fact multiple personalities at once (and in a couple of cases, switch them out for new ones).
So yeah, "insane and complicated" would more or less sum up this book. And I love it.