WHEN BOOK WORLD ASKED ME to review The PALADIN, it sounded, well, fun. Here was a novel about a special agent for Winston Churchill during World War II, by a smooth commercial writer -- a "big" book, with a first printing of almost 40,000 copies now on its way to the stores.

But as I read it, a bold statement by the publisher claiming that the novel was historically sound got the investigative juices bubbling. With my curiosity reluctantly piqued (a review is far easier than an investigative piece), I picked up the telephone and made an inquisitive call or two. What I learned is that, in important aspects, the publisher's claims about the book are false. Indeed, the author confirmed for me that on one extremely crucial point he had changed events for dramatic impact.

To call all this a hoax may be going too far. However, the most important events related in the narrative, the ones on which the publisher is basing its publicity campaign, are dubious. Some of them are even provably untrue.

In urging reviewers to take this novelcum-historical-fact seriously, Simon and Schuster says baldly, in a publicity handout:

"Here's the most shocking and astounding story of World War II -- The PALADIN by Brian Garfield:

"In 1940, Winston Churchill recruited a 15-year-old schoolboy to serve as his personal and secret agent . . . .

"'Christopher Robin's [code name for the young operative] wartime exploits included:

"--Rescuing thousands of Allied lives at The Battle of Dunkirk

"--Assassinating Admiral Darlan of France in Algeria

"--Preventing the United States from learning that the Japanese fleet was approaching Pearl Harbor

"--Insuring the success of the Allied D-Day invasion

"--Saving Great Britain from a Nazi U-boat blockade and possible starvation."

The publisher, in other promotional literature, goes on to say that while it can't prove incontrovertibly the book is precisely true, "We are convinced that no one can prove that it is not true." The major events "actually happened."

In a foreword, Garfield, a prolific American author perhaps best known for his novel Death Wish, thanks "Christopher Creighton" ("The hero of this narrative is a real person . . . . His name is not Christopher Creighton. This book is based on his extraordinary story . . . ") and admits that customary fictional license has been taken. However, Garfield assures the reader that he has done his best to ensure "there are no errors of chronological or historical fact."

If The Paladin were merely "faction," a time-sanctioned mishmash of what is fact with what is fiction (Verdi's A Masked Ball, Homer's Iliad, Robert Penn Warren's All the KING'S MEN are of the genre), there would be no occasion to criticize Simon and Schuster. But the publisher cites as hard fact explicit examples of British perfidy in World War II and makes other astonishing statements which, if true, belong on the front page, not the book review section.

Indeed, if parallel claims were made on a bottle of snake oil or an ersatz rubber tire, the federal government would be doing the reviewing and would step in if the claims were untrue.

And that is the second upsetting thing about all this hoopla. The federal authorities, quite properly, meddle only reluctantly with the printed word because of the First Amendment. All the more important, therefore, for publishers to avoid hyping their promotions so strenuously that it becomes false.

What Simon and Schuster claims is historically true, inter alia, is that an agent, at that time 17 years of age, was dispatched by a trusted underling of Winston Churchill (although without Churchill's knowledge) to sink a gallant Dutch submarine which had spotted the Japanese fleet approaching Pearl Harbor. The sub, says the book, had warned the British Admirality of the flotilla. Churchill's factotum, hoping Pearl Harbor would occur and thus bring the United States into the war, not only squelched the warning, but had the sub deep-sixed in order to cover up the evidence.

Futhermore, "Christopher Robin" is supposed to have assassinated three British officers who had handled the Dutch message. If all this is true, then not only were 56 Dutch submarines and the British code personnel sacrificed, but also the more than 3,300 Americans killed and wounded at Pearl Harbor.

In that case, Simon and Schuster's claim that this is "the greatest untold story of World War II" would probably be accurate, particularly when coupled with the other events in the book.

To comment in a general way, none of the claims made in the paladin could be verified by checks with the British Navy staff in Washington; the U.S. Army's excellent historical service; the Netherlands naval staff; William Colby, one of the most honest of our recent CIA directors; or an author to whom Colby and the Army referred us, Anthony Cave Brown, whose book, Bodyguard of Lies, dealing in depth with British intelligence work, was more than eight years in the researching.

These experts' comments on Simon and Schuster's claims varied from a mild "unverifiable" by the Army, to Colby's "I never heard of such a wild story" to Brown's "the whole thing is absurd."

While some of the claims, even if true, are, as Simon and Schuster states, unprovable, the sub incident, because of precise dating and locations, is particularly subject to investigation.

With the help of Dutch naval historians in The Hague, contacted by the Dutch assistant naval attache in Washington, Commander Jan W. van Waning, and of Van Waning himself who, fortuitously, is a writer on Dutch submarines during World War II, certain facts can be established.

The book claims the sub, then under British Admirality control, spotted the Japanese fleet at 0535 hours on December 2, 1941, headed for Oahu. Only two Dutch subs were under British jurisdiction at that time, the K-XVII and the O (forOnderzeeboot )-XVI (not "D" as the book says). Both came under the Admirality on November 28, 1941.

The O-XVI can quickly be ruled out as the sub in question. It was sunk by a mine, after sinking four Japanese transport ships, just northeast of Singapore on december 15, a week after the Paladin sub was supposed to have been sunk. Morever, the O-XVI had a survivor to tell about it. The K-XVII did indeed disappear, just as the book says, with no survivors. But on December 2, it was sailing toward Singapore. It left there on December 6, 1941. With a speed even on the surface of only 17 knots, it could not possibly have covered over 4,000 miles to Singapore from the ship lanes where it supposedly spotted the fleet. Nor could it have later reached the Fiji Islands where The paladin reports it sank December 7, 1941 (after, we are told, the teen-aged explosives expert gulled the Dutch captain out of his log).

Besides, records show that the British authorities were in radio contact with the K-XVII on December 10, and a meeting at sea occurred between the K-XVII and another Dutch sub on December 14, presumably near the spot in the China sea where it is thought to have gone down -- thousands of miles from the Fijis.

There are also problems with the details. The K-XVII had a complement of 38 submariners not 56. The "O" class boats, somewhat larger, carried only 40. The radio network for sending and receiving messages went through Singapore, not Brisbane or Auckland, as the the paladin states. And while the book claims the Dutch subs all went under British operational control after the fall of the Lowlands in May-June 1940, the fact is this did not begin to occur until more than a year and a half later.

Garfield, when confronted with this information, conceded he had made up the site and most of the details of the sub's sinking. He suggested that the Dutch sub in question was neither the K-XVII or O-XVI. So Commander Van Waning, an ex-submariner himself, checked and determined this time that no Dutch sub was near the Japanese fleet on December 2. All were in port or near the Dutch East Indies or, at the furthest, in the South China Sea, again thousands of miles from the Japanese carriers and battleships.

Garfield said he had depended on public records for his information and had not talked with any Dutch historians or authorities. Though he said he and the book's London editors had "grilled" "Christopher Robin," now in his 50s, Garfield at first told me they had not asked his collaborator whether the submarines was Dutch.

When it was pointed out that such an interrogatory failure was hardly "grilling," Garfield answered that they had simply forgotten to ask. He later amended this to say he had asked the question and that "Creighton" had confirmed the sub was Dutch.

Simon and Schuster, in a statement read over the telephone, seemed to be doing a bit of buck-passing by saying that they had depended on Bantam, the paperback house which had put together the book deal in the first place, and the English publishers, Macmillan.

"The major events described in the book actually happened," said the publisher. Every effort was made to ensure that historical events were portrayed accurately." All three publishers, affirms Simon and Schuster, did everything reasonable "to verify this story."

Yet the book project was well over a year in the making and, as far as Commander Van Waning knows, no one called the Dutch embassy to check out the book's most controversial allegation. Surely someone could have spared those 15 minutes before accusing an ally of such treachery.

And the book itself? The hero is a kind of Oliver Twist with submachine gun, at least a new wrinkle on the spy thriller. The writing moves along at a lively pace, but the characters are so wooden a Gepetto would drool. In sum, it's no Le Carre. Still, it's a substantial cut above, say, Robert Ludlum, whose own novels are equally improbable, but more clearly designated as pure fiction.