In the Novelverse, "Geordie" Kirk took an assignment as chief of security on Starbase 2, and exchanged letters with Jim...
In the '80s novelverse, which is a distinct continuity from the current one. Final Frontier
was based on the timeline of the Spaceflight Chronology
which put TOS in the first decade of the 23rd century rather than the 2260s. So it doesn't fit into the Trek universe as we know it today, for that and many other reasons. Such as that George is a redhead in the novel and brown-haired in the movie.
So we really don't know a thing about George Kirk in the modern continuity except what the movie established.