Decades after Captain Kirk is lost saving the Enterprise-B and presumed dead, Captain Picard finds him alive inside the Nexus, an extradimensional pocket of pure wish-fulfillment that a grieving scientist named Soran is willing to destroy entire stars to reach. Vornholt's young-reader adaptation of the film follows both captains stepping out of the Nexus together for one last mission, teaming up across generations to stop Soran before his obsession costs millions of lives.
Summary by Loreful, from public sources