This has been driving me crazy. There is a science fiction trilogy where the dead start coming back to life. It wasn't zombie fiction though.
In this trilogy, humanity has expanded to the stars, but then somehow the dead start coming back to life but they are "possessed" by different "Souls", so they are not zombies. There is an alien race that (atleast in the first book) knows the answer to why this is happening, but wants humanity to find out on its own.
Does anyone know which trilogy I'm talking about?