There was a very successful, very fannish series of Man from UNCLE official tie-in novels, mostly by the late David McDaniel (aka Ted Johnstone). The last novel ended up not getting published for various publisher reasons, and so the manuscript has apparently been kicking around Man from UNCLE fandom ever since.
You will notice some typical McDaniel features: the UNCLE arc story, which he created; the Tuckerized appearances of various real life friends of the author (such as author Stephen Goldin); and the Leibowitzed appearance of many fictional characters as real historical persons (allusions to Moriarty and to Nero Wolfe’s private detective associate, Saul Panzer).
Mr. McDaniel died young, so it’s nice to see that his friends and fellow fans have kept his work alive in this way.
J.M. Stine reminisces about McDaniel and his connections to The Man from UNCLE. It reveals the “true identity” of some of the novel-only characters; of course they were based on fannish friends!