In the 1960s and '70s, novelizations of TV shows or tie-in novels (featuring original stories based on shows) were very popular. In a time before recording, streaming and DVD sets, this was the only way (outside of reruns) to visit with characters you liked after the episodes had aired.
I don't know how publishers decided when to go with novelizations of episodes or when to commission original stories. Last year, I reviewed a couple of Starsky & Hutch novelizations, which featured stories adapting and expertly expanding hour-long episodes.
The Man from U.N.C.L.E. went with original stories. Different authors contributed to the 23 novels eventually published. Often, a common pseudonym would be used for each novel's byline. But in this case, each author is credited by his own name.
Apparently, the Man from U.N.C.L.E. books sold like hotcakes. Not many TV series, regardless of their popularity, racked up nearly two dozen tie-in novels.
I think one reason they sold was quality. The second book in the series was The Doomsday Affair, written by the prolific Harry Whittington. Whittington churned out scores of paperback originals throughout his career. Most of them are good and a lot of them are great. He worked in a number of different genres, with his hard-boiled crime novels and his Westerns being among his best works. Desert Stake-Out (1961), for instance, is one of the best Westerns I've ever read.
[SIDENOTE: The Doomsday Affair was one of the best-selling paperback originals of 1965-66 and went through multiple printings. Whittington was paid $1500 for the novel by the publishers and never saw a cent more. I'm very pro-capitalism and have no problem with a work-for-hire arrangements. But, for gosh sakes, if a book generates a fortune for your company, toss a nice bonus at the author!]
When he turned to U.N.C.L.E., he had Napoleon Solo and Illya Kuryakin racing to save the world. A bad guy known only as Tixe Ylno is planning on setting off an atomic bomb, starting World War 3, and then rising from the ashes to take over whatever is left.
I doubt there is a connection, but this was published two years before Ernst Stravo Blofield tried the same thing in the 1967 James Bond film You Only Live Twice.
The action picks up in Hawaii and Whittington starts out the novel with one of the best opening lines ever: "An instant before, she had been alive."
Solo had made contact with a woman defected from THRUSH, the evil organization that Tixe Ylno works with. But before she can tell him anything, a small bomb hidden in the lei around her neck explodes, killing her.
Solo is soon tracking down the person who gave the now-dead woman the lei. Illya is there as well, but the bad guys manage to arrange for him to be suspected of the murder, necessitating a jail break and an escape from both the cops and from THRUSH assassins.
Illya trails a villain to Mexico, while Solo tracks down a friend of the dead woman in San Francisco. Both end up getting captured. Illya's situation is particularly creepy. He's given a drug that causes him to move in spasmodic jerks and prevents him from speaking in anything other than inarticulate grunts. THRUSH agents walk him out of a hotel on the pretext that he's mentally disabled.
The climax of the book involves two failed attempts to escape from an insane asylum that's actually a THRUSH base, then one final effort to break out while the atom bomb is being loaded aboard a bomb. This last attempt is hampered by a fellow prisoner who has been brainwashed into killing Solo.
Whittington's prose is clear and the action scenes are exciting. The villains do grab hold of the Idiot Ball a few times--their justification for not simply killing the U.N.C.L.E. agents after capturing them is a little weak.
But those villains are otherwise top-notch in their villainy. Tixe Ylno's insanity is downright frightening. His top henchman is a sadist who deludes himself into thinking he's a scholar and an idealist. Both are great characters and legitimately scary at times.
Whittington effectly injects a hard-boiled edge into a novel based on a relatively light-hearted TV series. It is one of the best tie-in novels I've ever read.