In the vastness of the galaxy, the Culture society has explored new wonders. Byr Genar-Hofoen, an ambassador, is tasked with building a relationship between the Culture and the Affront. Meanwhile, an artifact has reappeared in the Esperi system, raising unanswered questions. Genar-Hofoen must leave his comfortable life to find the Eccentric ship "Sleeper Service" and its survivor.
On Phage Rock, Ulver Seich, a young scholastic overachiever, dreams of joining Special Circumstances and traveling the galaxy. When she is offered a secret mission, her dream may come true. Dajeil Gelian, self-exiled on the "Sleeper Service", faces her past and difficult choices when she encounters an old love.
As the ships' Minds of the Culture try to understand the artifact, it becomes the center of attention, drawing the interest of alien species and sentient intelligences. A deep conspiracy is revealed, which could lead to a new war. If not stopped, it could threaten the destruction of everything.
"Excession" consists of twelve parts, each divided into shorter chapters. Banks uses multiple narratives and points of view to develop the plot, creating a complex and engaging story. The large cast of characters, including humanoids, aliens, drones, and Minds, adds to the epic scale. Through this book, Banks shows us an incredible universe of unknown possibilities.