Developing and maintaining relationships, it's no secret, is not easy. No wonder a permanent segment of the publishing industry has been set up to guide the confused.

Although the function of these books is ostensibly to give advice, their real purpose is to provide reassurance. Such guides can convince readers of their relative normalcy: Lurking in the hearts of legions are similar hopes and apprehensions.

But you had a particularly bad time in the '70s? Again, reassurance: That decade, declare the authors of two recent manuals, was bleak and unromantic, littered with empty, unfulfilled relationships.

"While we were all dashing around acquiring notches on our headboards, we tended to lose sight of the human element: the caring, the consideration, the social communication," says Marilyn Hamel, 42, author of SexEtiquette (Delacorte, $13.95). "In our pursuit of the mantle of high-tech sex clinicians, it seems we've abandoned both the social graces and our sense of humor."

"The women's movement and the sexual revolution both took the romance out of relationships," says Michael Morgenstern, 32, author of A Return to Romance (Harper and Row, $10). "The sexual revolution made it easy to have sex with no responsibility, and the women's movement -- which had a good point -- said romantic gestures are nothing but chauvinistic trappings designed to treat women like objects. So men stopped making even the most basic courteous gestures."

Things are better now, claim Hamel and Morgenstern, because romance is back and manners are on the upswing. Which doesn't mean that the Protestant ethic theory of relationships doesn't still hold: It takes a lot of work on both sides for a couple to get along.

"There is an appetite on the part of the general public," says Hamel, "to get involved in something of more substance than testing their sex quotient.

"There's a greater emphasis now on establishing some sort of human rapport, something that ultimately will have some tenure. And in order to establish such a relationship, there are all of those amenities and niceties that go along with it."

Says Morgenstern: "Being romantic begins with one single, conscious decision -- that certain times during the week are unapproachable, because those are set aside to be with your loved one. It doesn't have to be something special -- even watching TV.

"But otherwise, with working schedules being as they are, it's possible to never see them. Especially with attorneys, who are working six or seven days a week."

Morgenstern speaks from personal experience. Once on "the typical lawyer track," the Hamilton, Ohio, native went to law school at American University, then got a job with a top New York law firm. At 29, he was "in the top 1 percent of credentialed attorneys at my age."

But the future seemed bleak: the emphasis on making partner, the hectic pace, the never-ending struggle to impress clients. He took a teaching position at Brooklyn Law School. Friends put him in touch with an agent who was looking for someone to write a book around the sure-fire title, How to Make Love to a Woman -- a title Morgenstern disowns -- and his career as a writer was launched.

One incident from this time still dogs his steps. He returned from a trip unexpectedly, walked in on his girlfriend, who was with someone else, and "for one split second, just lost it and pushed out at her."

The resulting court case ("It made great press") caused the expected amount of jokes and embarrassment. But he claims to have put the incident -- for which he agreed to pay the former girlfriend $30,000 in settlement of a civil lawsuit -- behind him.

"It humanized me," he says. "I think that people asked -- who is this guy that wrote this book? Who is he supposed to be, the perfect lover? I never said that. We do the best we can. I think what I did was wrong, and I paid for it. I've never done something like that before, and I never will again."

Hamel's route to SexEtiquette was simpler. Married at 19 and divorced 10 years later, the Canadian native is "a longtime observer and participant in the American mating dance . . . It was apparent that the choreography could use a little refinement."

Women, Hamel asserts, "have got to take the heat off men. Most men now view women as potential Xaveria Hollanders, ready to grade them on their erotic finesse. It's a little scary."

Her solution: Recognize that we're all experiencing the same anxieties, the same insecurities, the same doubts. And don't believe the media's view of what "our potential mate should be or what romance should be, as if it's something that should just suddenly come upon us and hit us between the eyes in some sort of marvelous hormonal explosion.

"Rapture doesn't disclose itself with the kind of dispatch we see on 'Dynasty.' "

The effect of their public persona on these writers' private lives isn't entirely positive.

His reputation, Morgenstern says, "can be a burden. When they hear the title, most people think of How to Make Love to a Woman as 'Hello, little lady, I've got a pocketful of change and I know how to thrill you.' "

More important, he says, "Researching A Return to Romance has taught me to expect lulls. Any relationship is going to have dull periods. I'm involved with someone right now, and with the kind of life style that I lead -- on the road Monday through Friday, for months at a time -- it's easy to let problems grow out of perspective."

Hamel says her son and daughter -- now 20 and 22 -- were initially "appalled that their mother was writing a sex book. It was clearly evidence that I was actually 'doing it' -- which is not something that any child wants to hear."

Currently living with a man, she's "a lot more thoughtful," she says, "about any of the issues that do come up, and a lot more open in tackling them instantaneously than letting them fester away, and letting petty resentments bubble up to the surface."

Personal satisfactions aside, plumbing the romantic depths is a profitable business each intends to pursue.

Morgenstern is working on a sequel, Making Romance Work. After that will be a volume on "the 100 most romantic places and events in America." Such as? "Going out to dog kennels." They're usually on a nice spot of land, he explains, and "seeing people pick out dogs -- it's just a fun time."

Hamel is working on SexEtiquette Retraining Manual for Gentlemen. "The very best thing that we've gotten out of the new morality is having choices. We have the option of being ourselves" -- and well-mannered selves at that.

So are we heading into a relationship happy valley?

"In the '70s," says Hamel, "there was the feeling that technical expertise was where it was at, and that anybody who didn't have a black belt in Kama Sutra was obviously going to be an incredible dud out there. But now I see us moving into a place where ultimately we can regard one another as individuals."

"Most men no longer do empty romantic gestures, or use them as a means to a sexual end," asserts Morgenstern. "It's not only a return to romance, it's a new romance. Most romantic gestures now are between people who have already had sex. It's what keeps the romance going."