I picked up this book when it was still on the shelves in the stores (remember those?). This is basically a "Man in a Hole" film noir story involving an honest to goodness PI (albeit a woman) in a city in a crater that's dangerously close to sunrise. The planet - thought to be tide-locked - is slowly turning toward the sun and when that too-close sun rises the city will burn.
This geographic item isn't simply back-story, it's the plot. Someone seems to think that the matter can be reversed, and is taking steps to make that happen. But they're doing that in a way that's attracting the wrong kind of attention. Things unfold at a good clip and get sticky fast. The tone and balance are excellent. I've re-read this one a few times.