Pym -- subtle and accomplished

It's easy to kill the book you love. Buttonhole a friend, exclaim over a book you've discovered, and before you know it you're the ancient mariner. And if you presume to tell your friends that Barbara Pym is the Jane Austen of our day, they'll probably grow cross, or glance at their watches and start shaking them. So I tread carefully when talking about Barbara Pym. I try never to compare her to the incomparable Jane, contenting myself with merely hinting that those who relish J.A. will appreciate B.P.

Barbara Pym, who passed on last year, wrote her novels between 1950 and 1978. When they first came out in England they made about as much splash as a rose dropped into a deep well. Then, in 1977, the Times Literary Supplement invited a panel of critics to name the most underrated writers of the past 75 years. Two of them chose Miss Pym. A.L. Rowse produced the ''Jane Austen de nos jours'' phrase (adapted by so many reviewers since), and Lord David Cecil called her novels ''unpretentious, subtle, accomplished'' and ''the finest examples of high comedy to have appeared in England during the past 75 years.'' So there.

No longer underrated, her books began to reappear, first in Britain and then (since 1980) in the United States.

Now with a hardback edition of No Fond Return of Love (E.P. Dutton, $12.95) nine Pym books have appeared in the US: ''Excellent Women,'' ''Jane and Prudence ,'' ''Less than Angels,'' ''A Glass of Blessings,'' ''Quartet in Autumn,'' ''The Sweet Dove Died,'' ''A Few Green Leaves,'' ''An Unsuitable Attachment.''

Pym's world is as limited (if ''limited'' is the word) as Jane Austen's. It is the world of middle-aged, educated gentlewomen with intellectual leanings, content to live alone, but not lonely, in villages or quiet London suburbs. They conceal a quiet sense of irony behind a conventional, often mousy, facade. Devoted to a certain kind of man in the public eye - a clergyman, an author, a lecturer - they are amused to find themselves involved in helping the object of their devotion with his work.

In ''No Fond Return of Love,'' Dulcie describes herself as one of those people ''who correct proofs, make bibliographies and indexes, and do all the rather humdrum thankless tasks for people more brilliant than themselves,'' dwelling on the words ''almost with relish . . . as if she were determined to create an impression of the utmost dreariness.'' A good way to brighten her life , she decides, is to fall a little in love with Aylwin Forbes, a biographer devoted to obscure poets.

So she does, and yes, it brightens her life, giving her an excuse to indulge a favorite hobby - researching (or prying) - into another person's life.

Whatever happens (and not much does) in this book, springs from the way the characters build situations in their heads. Obviously the author disagrees with her character, who feels life ''might be like a well-thought-out novel, where every incident had its own particular significance and was essential to the plot.''

For instance, when Aylwin's plans for a reconciliation with his estranged wife are ruined (''How could he enter the house with flowers for his wronged wife when the place was crowded with women buying and selling jumble in aid of the organ fund?''). He doesn't know what to do with the flowers, a bunch of chrysanthemums ''stiff and unnatural looking, like washing-up mops. . . .'' In desperation he bestows them on another devoted woman. So, unthinkingly, he has triggered a flood of unfounded hopes and speculation.

In the New York Times Book Review section, author Anne Tyler, describing books that have given her pleasure in 1982, asks, ''Whom do people turn to when they've finished Barbara Pym?'' The answer is easy: ''They turn back to Barbara Pym again.''

That's not such a dusty answer - Miss Pym's packed pages are well worth lingering over. There are passages in ''No Fond Return of Love'' I will want to savor again. Here are some of them:

On the end of a love affair: ''. . . later, when she was able to analyze her feelings, she realized that it was not her love for Maurice that had returned during their short meeting in the art gallery, but the remembrance of the unhappiness he had caused her. And that, she told herself stoutly, would soon pass.''

On self-deception: Grace Williton ''liked to think of herself as a straightforward sort of person. 'People always know where they are with me,' she would say rather smugly; it never occurred to her that people might not always want to know such things.''

And when I've finished savoring passages like that, what next?

Reread ''Pride and Prejudice'' of course. Jane Austen is never finished.