This is the fourth and final book in one of Bear's best series; Queen of Angels, Slant, and the short and forgetful Heads. Thankfully Moving Mars provides a suitably spectacular ending to the series, although like the other three, it's set some distance apart from the other books.
The social and political stresses between Earth, Mars, and within Mars itself are all detailed in the usual Bear style, complete with deep characters, scary weapons, and a decent pace that if you're not careful will keep you up late to read "just one more chapter".
Grab it if you can; it's not exactly one of the easiest books to get hold of.