Reddit mentions of Metaplanetary: A Novel of Interplanetary Civil War

These are all terrific, and are either obscure or all-but forgotten:

Evolution's Darling by Scott Westerfield

Stone by Adam Roberts

Broken Time by Maggie Thomas

Double Star by Robert Heinlein (forgotten classic, but still terrific)

The God of the Labyrinth by Colin Wilson (creepy, trippy, near-pornographic, but also mind-blowing)

Stations of the Tide by Michael Swanwick

Camp Concentration by Thomas M. Disch

Carve the Sky by Alexander Joblokov

Metaplanetary by Tony Daniel

Marrow by Robert Reed

In the year 2100, superhuman AIs will be disassembling the planets of the inner solar system to turn into computronium to add to the matrioshka brain. People we would probably still identify as human beings will have been pushed out to Jupiter or Saturn and will be living on giant floating islands. Most of their environment will be partially or wholly computer generated, and they'll spend most of their time in augmented or virtual reality. Giant lightsails carrying a tiny computronium payload containing virtualized minds will be sent out to explore nearby stars. Or at least this is according to Accelerando, one of the few sci-fi books to actually take the singularity seriously.

Alternately, the inner planets will be physically linked with huge cables, allowing interplanetary travel without spaceships. Colonies will be active on Titan, Triton, and most of the rest of the larger moons in the solar system. People will live between the virtual and real worlds, with aspects of themselves in both simultaneously. "Free Converts", which are consciousnesses that have been uploaded (converted) to be free from a physical body will be on the verge of being rounded up Nazi-style by a dictator who rules the most powerful and wealthy planet in the solar system: Mercury. The fully trans-humans will self-exile to the Oort Cloud and construct vast nanotech dust clouds that are simultaneously a spaceship and a body. Or at least that's according to Metaplanetary, one of the few other books that takes the singularity seriously.