"It's Your Body: A Woman's Guide to Gynecology," by Niels Lauersen, M.D. and Stevlogy," by Niels Lauersen, M.D. and Steven Whitney, published by Grosset & Dunlap, 562 pgs., $8.95 paperbacks.

He recites the horror stories. Like the one about a 25 year-old woman who underwent an unnecessary hysterectomy, had her ovaries removed and a colostomy performed in the process.

While Dr. Niels Lauersen stresses that such an incident is extremely rare, it illustrates dramatically his reasons for writing "It's Your Body: A Woman's Guide to Gynecology".

"I was unhappy about the care women get," says Dr. Lauersen, 38, a gynecologist, researcher and professor at New York Hospital - Cornell University Medical College.

He doesn't, however, put all the blame on doctors. Too many women are passive or uninformed consumers of gynecological care, contends Dr. Lauersen, who calls his book "an encyclopedia for women . . . like Dr. Spock wrote for babies."

"The gynecologist is your partner, not an omnipotent medical seer," he says. "So much could be improved if women knew more about their bodies. I'm saying you should treat yourself . . .but it's important to offer the gynecologist the best information you can about your condition. Seek information. Ask questions. Get to understand what the doctor is doing with your body."

Lauersenhs book begins with an illustrated chapter on self-examination and concludes with a section on sex throughout various life stages. In simple, direct language he tells what is happening on the other side of the stirrups during pelvic examination, discusses various contraception methods and explains common surgical procedures and tests.

His lack of sexism or condecension has drawn praise from feminists who applaud the book's focus on helping a woman make informed decisions about her health care.

This emphasis extends to a section, titled "How to Examine Your Gynecologist." Here are some of Lauersen's suggestions for choosing one:

Seek advice from your family doctor or trusted friends. But remember that the doctor who is good for your mother or your best friend may not be the one for you.

Get suggested names from the nearest good hospital, preferably one associated with a medical school, or from a local planned parenthood chapter or medical society.

If you have a particular problem, infertility for example, ask for doctors with a subspecialty in that area.

Look up doctors in the Directory of Medical Specialists, available in may public libraries and at local county medical society offices. Their medical school, residency, hospital affiliations and board certifications are listed.

Seek out a gynecologist, male or female, with whom you can discuss problems easily. Bring up your personal needs to determine if the two of you philosophically compatible. You should find out the recommended doctor's opinions on such matters as abortion, birth control, estrogen therapy or any other topic which concerns you.

If a gynecologist is cold or unsympathetic, rushed or disorganized you should probably look elsewhere.

Call the doctor's office and compare fees for the initial vist and examination. The best doctors don't necessarily charge the most.