In her eye-opening memoir Mad Women: The Other Side of Advertising in the '60s and Beyond, advertising veteran Jane Maas pulls the curtain back on the reality behind the hit series Mad Men—that is, the advertising industry in the 1960s, when she worked as a copywriter at Ogilvy & Mather in an era of “casual sex and professional serfdom.” A “real-life Peggy Olson,” her story is sure to keep fans of the series sated at least until the March 25 season five premiere. Here, publisher Thomas Dunne shares a passage from chapter two, “Sex in the Office.”

As soon as people find out that I actually worked at an advertising agency during the Mad Men era of the 1960s, the first question they ask is “Was there really that much sex in the office?”

The answer is yes. Copywriter Linda Bird Francke started her career at Young & Rubicam, said to be the prototype of Mad Men’s Sterling Cooper agency. Linda told me: “I was in the typing pool, and I lost my virginity to the account executive on Jell-O. He was immensely charming, a Hungarian who had been a professional soccer star, came over here to play a game, and managed to defect. I was smitten. He took me to his apartment one evening after work, and we had sex. Then his telephone rang, and I could hear a woman crying and accusing him of being unfaithful.

“Pretty soon after that I figured out he was working his way through the typing pool. So somebody or other in the pool was always crying because she suspected he was sexually involved with somebody else. And she - - whichever one she happened to be - - was always right.”

According to eyewitnesses at Y&R, the Hotel Lexington was a favorite trysting spot. It was just a few blocks from the agency, and the front desk clerks didn’t raise an eyebrow when you asked for a key at noon and returned it at two. If you met fellow staff members coming through the lobby, you simply averted your eyes.

Office parties were always a sexual hazard. It was said that no virgin ever returned a virgin from the Ogilvy boat ride, the wildest event of all. It was a cruise around Manhattan Island, to which everyone at the agency was invited. This annual affair was an orgy of heavy drinking and fairly overt sex. At least it was annual until the office manager got so drunk on one cruise that he fell overboard. He was fished out, none the worse for wear, but Ogilvy management weighed anchor on the boat ride.

It seems to me, looking back at all the marriages breaking up because of sex in the office, that it was primarily the most senior men in my agency who were having the serious affairs. Why? First of all, they had big private offices with doors that locked. And couches. (Junior account men just had chairs.) They had the money to reserve hotel rooms or take off for a weekend.

More important, though, was the fact that these executives gave the agency a higher priority than they gave their marriages; they were devoted to their jobs and worked late four or five nights a week. One man explained it to me this way: “By the time we got home to Connecticut or Westchester or wherever, we were beat, our wives were sleepy, and we didn’t have much energy to talk, much less make love. It was a collision course.”

A former agency head, now in his nineties, told me, with a twinkle in his eye, that he couldn’t resist. “I was forty-five years old, and for the first time in my life I was getting blow jobs in the back of a car. I left my wife and married the girl.”

From Mad Women: The Other Side of Madison Avenue in the ’60s and Beyond by Jane Maas, Thomas Dunne, Copyright © 2012