A Matter of Life and Death : THE LATE NIGHT MUSE, <i> By Bette Pesetsky (Harper/Collins: $19.95; 272 pp.)</i>

Terminally ill people keep secrets. They live alone. They look at us from a great distance, as if to say, “Don’t ask for too much.� Alone with their disease--virtually down inside its maw--they reflect. They stew. They take time to imagine the unthinkable: a future--tomorrow, the day after--without them in it. For all of these reasons, people who know they haven’t long to live make for intrinsically captivating fictional exploration, especially as narrators.

In Bette Pesetsky’s new novel, “The Late Night Muse,� the main character, Bernadette Marrkey, has been diagnosed as having a fatal disease of the nervous system. From the symptoms and the history here described, the disease resembles multiple sclerosis, but Pesetsky never quite names it. This is a smart move, as it saves both author and reader from the unavoidable tedium of waiting for the next symptom to appear--an inherent risk of the genuine disease book, which this novel certainly is not. At the novel’s opening, Bernadette, our narrator, a woman in her late 30s, is in the fifth year of her illness.

A reader familiar with Pesetsky’s fiction will know better than to expect self-pity or easy tears, even when the material might lend itself to a tragic and self-dramatizing perspective. Pesetsky is nothing if not smart and sharp. Her prose has snap and vigor, her ear is excellent, her insights dazzle. She can be too clever, but she is never lazy. As she is particularly good with women characters on the verge of some big move, this new book is right up her alley.

The novel is organized by means of, first, a medical questionnaire that Bernadette Marrkey’s doctor has asked her to fill out, regarding the basic business and progress of her disease. Questions include, “How do you perceive your illness?,� “When were you absolutely certain that you were ill?� and “Do you understand the nature of your illness?� The questionnaire gives Pesetsky a chance to invite Bernadette’s sharp tongue to indulge itself, as well as to fill us in on her past--Bernadette having realized long before the doctors that something serious was wrong with her.

The other things we find out immediately about Bernadette are: She is a poet, not a well-known poet, but still; she has been published in small-press magazines called Seltzer, Sign, smack and vanish; she’s serious; she seems to have the heart for writing and the necessary penchant for a secret life.

When the novel opens, Bernadette is organizing her own archives. As 1985 is the year she has decided she will probably die, she is taking the remainder of the year, some 11 months, to pack up the stuff of her life in boxes--12 dozen of them--so that after her demise, the “artifacts--the leavings of the artist� will remain. The novel is the story of how the Marrkey archives come into existence.

Now Pesetsky is no A. S. Byatt and this is no “Possession.� If anything, “The Late Night Muse� is a send-up of what may be called the archival novel and for an obvious reason: Bernadette Marrkey may be sick, but indubitably she lives.

Journals loom large. A writer, Bernadette insists, must have journals. But Bernadette has never kept journals, and so she makes them up, backdating the entries, creating her own archives, making up a life--her own--as she goes. “How,� Bernadette writes, “does anyone know that they are destined to be remembered? . . . Others can present for their archives such a complete accumulation of their existence. . . . Where did they save them? Weren’t their apartments ever too small? . . . I mean you can’t collect this stuff retroactively, can you?�

Which is exactly what Marrkey does, collects retroactively, filling us in as she goes on the sometimes hilarious and always moving events of her life. The 144 cartons--variously described as a Hoover Dam, a Chinese Wall, a mountain range of boxes--are her final revenge--on her husband and children, who cannot bear to take her life, her illness or her work seriously.

Bernadette Marrkey is a lovable lunatic--one of us --a woman who is out for nothing less than making art out of a not-so remarkable life. In “The Late Night Muse,� Pesetsky is doing what she does best, tackling a number of extremely difficult life-and/or-death issues with energy, wit and freshness. She has loaded a great deal of life and liveliness into this very entertaining, altogether serious novel.