Call it a case of Sperm und Drang.

Warner Books announced that it is recalling 115,000 copies of Dr. Ruth Westheimer's "First Love: A Young People's Guide to Sexual Information" after a typo was discovered, telling teen-agers the safest time to have sex was during a woman's most fertile period.

"Even big shot people like myself make mistakes," a sheepish Dr. Ruth said yesterday, adding that she was "genuinely upset" over the incident.

The error appears on Page 195 and was discovered by a Ramsey, N.J., librarian last month. Ann Scarpellino, the mother of three, said yesterday that after purchasing "First Love," cowritten by Nathan Kravetz, she took it home to read before placing it on the library shelf. The error appears in Chapter 10, and says, "The safe times are the week before and the week of ovulation."

"Obviously," said Scarpellino, "it was meant to be 'unsafe.' It sounds like a typo."

She called the publisher and said there must be a mistake. The publisher agreed. Last week, Dr. Ruth -- the country's best-known sex therapist, who hosts a radio show and a cable television talk show -- called the librarian. "She said she'd spent a sleepless night. Her editor was in tears. She thanked me for about a half an hour."

Said Dr. Ruth, "I invited her to have lunch with me."

The sex therapist also said she had read and approved the manuscript with the offending line. She can't explain how the error occurred. "In my mind, I read 'unsafe.' I didn't catch it."

Warner Books, said Scarpellino, "really bent over backwards" after learning of the mistake. The publisher is urging consumers to return the $3.50 paperback to the company for a corrected version, due out this month.

"Thank God not too many have been sold," said Dr. Ruth.

Warner spokesman Barbara Uva said yesterday the manuscript went through the usual editing and proofreading channels.

While saying she "thinks very highly" of Dr. Ruth, the diminutive diva of "good sex," Scarpellino called the misinformation "the worst mistake that could have been made."

"The interesting thing is," said Dr. Ruth, with her characteristic giggle, "some reviewer for a library journal reviewed the book and said it was medically correct. She didn't like the book, but said it was correct."

Warner Books said it had not heard of any untoward consequences -- yet.

"Lawyers have been on the case," said Uva. "We hope we won't have to deal with that."

"Good heavens," shrieked Dr. Ruth. "Don't even mention that! It would give me more sleepless nights."