The story itself is almost Clancy-esque - Johan Eschbach is a former member of the Spazi (CIA equivalent) and a former member of the government who is now teaching Environmental Politics at a University in a backwater town. I suspect if I had more knowledge of East Coast US towns I'd recognise this one - it has that feel of 'look how this is just off kilter'. Eschbach is trying to get on with his life now he's left his governmental (and other) work behind, but when another Professor at the university is murdered he gets drawn back in against his will.
Overall I did like this, and enjoyed reading it - but it didn't quite gel for me. I found the alternate universe extrapolations distracted from the story at times (even though ghosts were integral to the plot), and I didn't entirely agree with them - I think because he'd kept too many of the names the same. If the population growth has been totally different over the whole of human history why would there still have been a Babbage at roughly the right period of history? And why would this Babbage still have invented a difference engine? Why given all the differences in the history in the American nations would there still have been a Roosevelt in power at roughly the right time? I can see that using those names kept it closer to the real world, and gave it that alternate history feeling, but it made it seem more contrived to me. And made it seem a bit more like the plot & device were both conceived to carry the message of eco-friendliness that a lot Modesitt's science fiction seems to carry. And I'm not that keen on having Message beaten over my head.