Excession

A Culture novel by Iain M. Banks. When an enigmatic object, the Excession, appears near a remote star, apparently beyond anything the Culture's technology can explain, its Minds argue over how to respond. Diplomat Byr Genar-Hofoen, posted among the aggressive Affront, is sent to recover the stored mind of a starship captain who encountered the object long ago, and is swept into a conspiracy that could lead to war.