The writer, Frank Tarloff, was a talented comedy writer who was unable to get his career off the ground due to the blacklist. Producer Sheldon Leonard hired him to write TV scripts, including several "Andy Griffith Show" and "Dick Van Dyke Show" episodes, under the pen name David Adler (a name he continued to use for some of his TV work even after he was no longer blacklisted). "Guide," released simultaneously as a movie and a tie-in book, was his biggest success.
As the article makes clear, Tarloff's original idea for the film was to make fun of wives who get cheated on; director Gene Kelly had him change the tone of the film so the philandering husbands were the butt of the joke -- though perhaps I shouldn't use the word "butt" given director Kelly's fixation on the female posterior (or as Pauline Kael put it, "bottoms and bosoms that look like bottoms"). And of course, in true '60s sex-comedy fashion, there's hardly any successful adultery and none at all on the part of the hero.
The film sort of divides people, some finding it unfunny and stupid, others finding it... well... funny and stupid. I'm in the latter camp. Kelly wasn't much of a director, at least not when he wasn't co-directing with Stanley Donen, but he does keep the movie moving very fast, much faster than most '60s comedies, which tended to be stodgy. The borrowings from the French New Wave, de rigeur at the time, are transformed into a then-new, now-common device: the quick cutaway to a comic fantasy sequence. Every few minutes, Robert Morse will be talking about a guy he knew or a problem a would-be adulterer can face, and the movie cuts away to a segment illustrating his point; the segments range from five-minute sketches to ten-second gags. Breaking up the linear story for the sake of a quick gag is common now; "Family Guy" does it badly and shows like "Arrested Development" do it well. But it was pretty new in 1967 story-centred comedy. And Kelly finds ways to keep the material from being offensively sexist; it's so silly, and the husbands are mostly such fools, that it's more inoffensively sexist. Still, while I'd recommend checking out the film, I wouldn't recommend trying to make too many excuses for its sexual politics; the innofensiveness of its sexism just means that it's better than, say, M*A*S*H (another successful Fox movie scripted by a formerly blacklisted writer), not that it's not kinda Paleolithic.
The zillions of star cameos are, inevitably, hit-and-miss; the best sequence is probably the famous one where Terry-Thomas commits adultery with Jayne Mansfield, and then they can't remember where she put her bra.
Terry-Thomas: "I'm worried about my wife coming back and finding it."
Mansfield: "She'll just think it's one of hers."
Terry-Thomas: "Don't be ridiculous."
Another good sketch, if overlong, features Carl Reiner basically repeating his Alan Brady character from "Dick Van Dyke," trying to romance a pre-Planet of the Apes Linda Harrison without his wife or the tabloid press finding out.