Cohen, the Jewish cyber-sybarite, has travelled to Pittsburgh to commit suicide. A Pittsburgh on another planet, not Earth's Pittsburgh. As the first book was sort of set in a Welsh coal mine in space, this one is a run-down blue-collar steel town. In space.
That's kind of cool; the problem is the background, which is relentlessly recapped and yet still somehow unclear. Ever since the coal mines blew up in the first book, FTL has been on the way out -- it was FTL coal -- so Earth's colonies are scrambling to achieve some kind of self-sufficiency before space travel becomes impossible. Only it's not becoming impossible, it's becoming... pirates. In space. Everyone is looking at the Drift, an area of space where FTL will either remain possible or has never been possible because of multiple universes. There are pirates there.
This book would have been pretty awesome if I understood what it was about.
In fact it doesn't deserve that much snark. It was pretty good regardless. Catherine Li (Cohen's wife, a human being) has to travel out to Space Pittsburgh -- via a form of cheap, dangerous FTL which either does or does not require space coal -- sorry -- anyway, she winds up forked in a quantum teleportation accident. (It took me three-quarters of the book to figure this out, but that isn't the author's fault. I was just dumb. Two alternating plot threads: two Catherines.)
She winds up on both sides of a space pirate feud, while trying to find Cohen and ask him why he killed himself.
This book is a serious attempt to tangle with how different AIs might be. Cohen is a distributed network of software agents; "death" is a disintegration, but leaves sentient fragments and shadow-Cohens all over. (In fact we meet an AI who used to be part of Cohen but seceded.) Then of course we have the bimodal Li. So this is excellent SF idea-wrangling. And the story has lots of stuff going on, what with the pirate captain and the blue-collar cop and the scary bad guys closing in everywhere. I just... couldn't get oriented, through the whole book.