Bigamy

Question masters were instructed to "accept any similar wording".

While it's true that this aphorism appeared in Fear of Flying, it's not correct to describe it as "a quotation from [that book]". It was included as an anonymous epigraph.

It has also been attributed to Oscar Wilde (with the word "wife" substituted for "husband", but he probably didn't coin it either. Similar remarks are however recorded from at least as far back as 1897, when a book entitled Reflections of a Bachelor, by "P.W." (Post Wheeler) included this: "Lots of men who aren't bigamists have one wife too many."

Further details can be found on The Quote Investigator.