There is one funny moment in Ring Lardner Jr.'s new novel "All for Love."

Jeremy Singer, the scientist-hero of the story, has invented a drug he calls Eroticin because it has the power to stimulate the feelings of love in those who receive it. The object of the love will be the first person encountered after the treatment. As a test, Jeremy administers the drug to his pious Hispanic housekeeper, who goes upstairs, thinks about Christ, realizes that she can be happy only by becoming His bride, and promptly reappears on the stairs, suitcase packed, ready to check in at a convent.

That's the only funny moment in the novel and, truth to tell, it's not really all that hilarious. The reason it's amusing at all is that it grows out of both character and plot, elements that seem to make greater demands on the comic writer than on anyone else.

Lardner must have had a bad few weeks while he was working on this little book. After all, we know he can write. He is the author of "The Ecstasy of Owen Muir" and "The Lardners: My Family Remembered." He is also a screenwriter, with "Woman of the Year" to his credit. And we know that he can be wonderfully funny; he also wrote the screenplay for "M*A*S*H."

The premise of "All for Love" is, if not wildly inventive, at least promising. Jeremy, a brilliant scientist but a dismal failure with women, concocts Eroticin in order to win his dream girl, one Loretta Kane, an Olympic medalist and later a Hollywood beauty. Never mind that by the time he gets to her she's hitched to a rising political star. Jeremy wins her -- if that's the word -- by slipping her the drug, then loses her, and in a desperate effort to regain her, ends up at a Camp David summit conference (Loretta has remarried her ex-husband, who is now president, see?), and while explaining how the United States can overcome Russian aggression in a mere 20 years, he slips the drug into the punch, but as things turn out . . . Well, it's all pretty confused.

Comedy requires that the writer be in absolute control of his material. And the funnier it's likely to get, the more manic and frantic, the greater the control required to pull off the comic effects. Lardner simply isn't in control.

The passage of time, for example, is merely bewildering to the reader; years go by sometimes in a blink, although hardly in a twinkle. New characters appear, complete with backgrounds, two-thirds of the way through, and then disappear on the next page. There are several lengthy, and singularly unfunny, scientific lectures. We are told all sorts of things we never wanted to know, such as details of the lovely Loretta's bodily cycles. And all about the sexual habits of coyotes. Yes, coyotes. And so on. It's all a terrible, terrible muddle. That's one of the book's major problems.

Comedy also requires exquisitely careful writing. You have to be precise to be funny. Lardner is careless in both his thinking and his writing. For one thing, he makes the same mistake his character does in confusing love with sex, and his single comment about this comes 100 pages too late. He accepts at face value, and seems to identify with, his characters' shallow thinking, such as Jeremy's scheme to overcome Russia, a scheme that manages to be both tastelessly cynical and breathtakingly naive.

And sometimes the writing itself just doesn't mean much of anything: "Jeremy noticed how much (the coyote pups) looked like domestic dogs of the same age, much more like some breeds, in fact, than those breeds resembled certain other ones." How's that again?

There are plenty of faults to examine here, but one in particular -- Lardner's failure to distinguish his own thinking from that of his characters -- points up a basic truth of comic writing. It is perfectly acceptable for a character to be mean or thoughtless or shallow or tasteless or cynical; that can make for satire, laughs, good fun. But it's definitely not all right for the writer to be that way. We have to be able to trust the writer as a reliable guide to the follies of his characters.

We could always trust, among our comic novelists, Max Shulman and Jack Douglas. We trust Peter De Vries. We trust the British: Tom Sharpe, William Boyd, Clive James, Keith Waterhouse, Malcolm Bradbury. This time out, at least, we can't trust Ring Lardner Jr. as far as we can trust his unsavory little hero. And that's not far at all.