Is Sex Necessary? is a 1929 book written by E.B. White and James Thurber. It deals humorously with sexuality and romance, in a way that I assume must have been at least somewhat titillating in yon days. Part of the books humor apparently comes from the fact that around the time it was written, books on marriage and sexuality, written from the viewpoint of the newfound science of psychology, were a cottage industry. I have to admit that from my 2009 viewpoint, the specific zeitgeist that inspired this book is not in my background knowledge.
Which brings up why this book is funny to me: it would seem that whatever witticisms and coy comments about sexuality would appear amusing to an audience in 1929 would fall on deaf ears in the jaded 21st century. I have had my mind scarred by mention of every perversion and depravity known to humankind, and that was just going through my spam filter this morning. But strangely enough, while reading this book, I did not find it quaint. When reading about the flappers who moved to New York City from Ohio to become liberated, but who instead spent their time decorating lampshades, my mind instantly translated it into hipsters who moved to Portland from Ohio to become polyamorous and bisexual, but instead spend most of their time making vegan bread. Cue Dickens: "in short, the period was so far like the present period", that most of what applies then applies today.
Of course, the book should not totally be taken as a serious sociological work, although it is actually a pretty good source of background information on what people believed---or didn't believe---80 years ago. But on the whole, this book is meant to be read for humor. That is why it is a humor book.