I'm looking for the name of a space horror novel from 1990's (I think) where the dead go to a very overcrowded limbo, and then the worst of them escape and possess people and start to take over a planet. Also features augmented mercenary soldiers who battle the possessed and a secondary storyline on a mega rich space ship.
This has to be the Night's Dawn trilogy by Peter F. Hamilton!
The sprawling narrative deals with a far future where humanity wages war against past souls flooding back into the land of the living via possession (Al Capone and Fletcher Christian are among the returnees). Hamilton's future is expansive and primarily optimistic, with huge sentient space-cities that can closely resemble a natural Eden.