Consider Phlebas
The opening novel of the Culture series, a space opera about a shapeshifting mercenary caught between the Culture and its enemies during an interstellar war.
Set during the Idiran-Culture War, the novel follows Bora Horza Gobuchul, a Changer who has allied himself with the Idirans against the utopian, machine-governed Culture he considers dangerously naive. Horza is dispatched on a mission to recover a renegade Culture Mind that has taken refuge on a forbidden world, drawing him and a crew of mercenaries into a series of increasingly desperate schemes across a galaxy at war. It's Banks's first published science fiction novel and the introduction to the Culture universe.
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