The Quiet War by Paul McAuley
This is a science fiction novel about low intensity conflict set in the 23rd century a.d.. Earth is ruled by a set of rich families who are trying to fix the environmental depredations of the previous centuries. Brazil is the rising military power.
On the opposing side are the democratic colonies of moons of Jupiter and Saturn. Mars was previously in a conflict with earth where the martian colonists were wiped out.
Both sides have strong ideological differences. There is spy craft, subterfuge, sabotage, and political maneuvering which eventually leads to full scale war.
The novel is hard science fiction. The author, Paul McAulety is a botanist by training; he includes a bit of biotechnology and ecological engineering. This makes the descriptions quite interesting. This is especially true of the descriptions of the Brazilians trying to clean up a despoiled earth.
My favorite character is Macy Minnot, a biome technician, who is caught up unintentionally in the conflict and does some very entertaining heroics. The ending makes me wonder if there will be a next novel. If there is I will definitely read it.
Paul McAuley has been nominated for the Arthur C. Clarke Award, is on the 2008 Locus recommended reading list, has won the British Fantasy Award, the Philip K. Dick Award, and is a wonderful writer. His website is http://unlikelyworlds.blogspot.com