ARE YOU quite sure, Superintendent?", the suspect challenges. No, Scotland Yard Supt. Richard Jury is not quite sure. Neither is the reader when he comes to the end. And that is what makes the latest mystery from the much-acclaimed Martha Grimes such an exasperating and irritating book. It is, in a phrase that Grimes herself uses, "ambiguous to the end."

Is someone impersonating someone else impersonating himself? I cannot guarantee you'll know the answer for certain when you finish The Five Bells and Bladebone (Little, Brown, $15.95).

Remember how the wily Agatha Christie had the preening Hercule Poirot assemble suspects and participants in the drawing room to explain the diabolically clever twists he had unraveled to reach a solution? Oh, how one longs for such a scene at the end here, hoary device though it may be.

In The Five Bells and Bladebone, the ninth in the pub-named series, Jury is on holiday and goes to the village of Long Piddleton to visit his friend Melrose Plant, an amateur detective and one-time nobleman who quixotically gave up his title. All the old gang is there, including the outlandish Marshall Trueblood, who runs a posh antique shop and finds a bloody corpse stuffed in the secre'taire a` abattant that he has just purchased.

It is the body of Simon Lean, the philandering husband of Hannah Lean, granddaughter of dowager Lady Summerston and heir to the Watermeadows country estate and family fortune.

Hannah, the wronged wife, rather plain and mousy, is the local constabulary's prime suspect. But it it is Jury who links Simon's murder to another homicide 50 miles away. Police believe that victim is Sadie Diver, a street-smart gal who seems to have come into money in the last two months.

How the plot does thicken! Witnesses confuse photos of the corpse and of Hannah and Sadie, who bear an uncanny resemblance once the street girl's tarted-up makeup is removed (echoes of the identity question in Josephine Tey's Brat Farrar).

If the murders in Long Piddleton and London are linked, there are endless possibilities. Is there a double murderer or did separate culprits perform the deeds? Who plotted to kill whom? Who murdered whom and in what sequence? Has one of the murderers become a victim? And who is the "Hannah" at Watermeadows? Permutations and combinations.

I did manage to work out a scenario after sorting out a crime scene overpopulated with people and littered with red herrings and irrelevancies, but Grimes should remember that a mystery should not be "ambiguous to the end."

Making Book

YES, THERE is something to be said about the light-hearted and perky mystery with a straightforward storyline that leads to a modest surprise at the end.

So welcome back to Charles Goodrum with his third mystery novel, The Best Cellar (St. Martin's, $13.95), a diverting exercise in scholarship-cum detection. Seldom has historical research been so intriguing and exciting.

Goodrum, author of Dewey Decimated and Carnage of the Realm, brings along his engaging trio of amateur sleuths from the fictional Werner-Bok Library -- Crighton Jones, who handles the library's public relations; Steve Carson, young archeologist and Crighton's persistent admirer; Prof. Edward George, retired from the library director's office but not from life. Like all amateur sleuths, they stumble over a body or two and find themselves in the middle of a murder investigation.

Crighton offers her spare room when a Library of Congress colleague asks for help in finding temporary housing for an out-of-town researcher. Durance Steele, a chic, sophisticated young woman who is secretive about her research project, drops enigmatic hints that she may have found a "real time bomb in one of our national myths" and that the discovery could make her both rich and famous.

The next morning, she drives off in her red Porsche and disappears. There is a threatening phone call and then a card with bloody red ink.

Crighton, Carson and Prof. George check with friends in scholarly circles and discover that Durance may have stolen a thesis idea from her University of Virginia roommate. It turns out to be a dangerous coup for Durance.

The mystery in The Best Cellar turns on a curious footnote to history: What happened to the 3,000 books of the original Library of Congress when the British burned the Capitol and the White House in 1814?

With convincing documentation, Goodrum points to speculation that Jefferson's friends may have hidden the books so that Jefferson, deeply in debt, could sell his personal library of 6,000 volumes to the government for $23,950, a princely sum at a time when a skilled carpenter earned only $300 a year.

What had Durance found out about the books? The sleuthing trio tries to track down where they might have been hidden more than 170 years ago. Since there was a traffic jam at the Pennsylvania Avenue bridge over Rock Creek on the way to Georgetown as residents of the capital fled in panic before the advance of the British, they speculate that the oxen cart carrying the books probably used the Long Bridge (an early 14th Street span) to escape to the Virginia countryside beyond Alexandria.

Their search leads to the Belvoir mansion, seat of the Fairfax family. There they find Durance's red Porsche and her body.

Goodrum makes scholarly research as thrilling and suspenseful as any car chase or cliffside confrontation. The motivation is not exactly compelling, and perhaps young people don't talk like Crighton and Steve any more. Still, theirs is charming banter, and when Goodrum uses a four-letter word, it is painfully out of sync.

Goodrum, who retired from the Library of Congress in 1978 as director of planning and development and is the author of Treasures of the Library of Congress, is a man of learning and curiosity. He supplies a wealth of fascinating tidbits of information on such topics as archaeological measurements, a Herculaeneum clothes press, the market for rare books, examples of printing before the Gutenberg Bible, and colonial architecture.

The Best Cellar may be talky, but the conversation is fascinating. It's a charmer.

Bay Bridge Blues

NICK POLO is still another California private eye, and Polo Solo (St. Martin's, $13.95) traverses the familiar big-city scene -- drugs, porn flicks, seedy street hangers-on, dirty politics and sadistic thugs.

Nothing new, it is true. Yet Jerry Kenealy does it well. He writes crisply, brings alive the streets of San Francisco, and plots cleanly and interestingly. Polo, a shamus who has been in jail on an embezzlement charge after he bends the law, doesn't overdo the macho bit and is a breezy, relaxed narrator.

Of course, there's a lot of violence (a vicious Doberman is one perpetrator) and a slam-bang confrontation before Polo finds out who masterminded the plot to derail Mayor Barbara Martin's bid for a Senate seat by blackmailing her with a porn video tape taken while she was drugged.

Kennealy, who is a private investigator himself, includes some nifty tips from a pro, including how tho hide a gun in the headrest of a car.

Behind the Mask

THE POPULAR Charles Paris, the endearing roue' and actor-sleuth of Simon Brett's theatrical mysteries, is back on the boards after "resting" -- an actor's euphemism for unemployment between jobs -- while Brett introduced a new sleuth (Mrs. Pargeter in A Nice Class of Corpse) and wrote his second psychological thriller (Dead Romantic).

In What Bloody Man Is That? (Scribner's, $14.95), Charles is bored with "resting" and jumps at an offer to play multi-character roles in a provincial theater production of Macbeth. Everyone knows the "Scottish play" is bad luck. No one dares utter the word "Macbeth" within the confines of a theater.

The Pinero Theatre production proves to be extremely unlucky for Warnock Belvedere, the actor playing Duncan. He is found dead in a storeroom, suffocated by carbon dioxide escaping from a ruptured line carrying the gas to pump beer to the theater bar upstairs.

The discovery is made by Charles, who has blacked out himself in his dressing room after downing too many Bell's whiskies. For Charles, it is a sobering experience, particularly when the police view him as a suspect. He gives up whiskey for distasteful Perrier water.

No one liked Belvedere, a mean-spirited, vulgar man not above seducing a schoolboy. Charles has two reasons for wanting to solve the case quickly: To clear himself and fulfill his vow to find the real murderer before he takes another drink. He feels a sense of urgency on both counts.

Brett views the theater world with affectionate humor. He can be wickedly witty when he takes aim at some of its absurdities and pretensions.

There is the young, intense actress, fresh from the Royal Shakespeare Company, who believes sex spoils her concentration while rehearsing and performing and can spend hours discussing the interpretation of Lady Macbeth's reference to "the milk of human-kindness."

In one hilarious scene, rowdy boys and girls come to a School Matinee to pounce upon any line with sexual overtones. "Come to my woman's breasts," says Lady Macbeth, and the theater is filled with whistles and giggles.

And then there is Charles, struggling to keep up with costume changes as he plays the Bleeding Sargeant, Drunken Porter, Sewer, Old Man, Scottish Doctor, English Doctor, Apparition of an Armed Head, and two soldiers on both sides in the battle of Birnam Woods. Lay on, MacBrett.

Jean M. White reviews mysteries for Book World the third Sunday of every month.