David Niven was known for wit, charm and his willingness to take almost any movie job that came along. This meant he made a lot of turkeys, though once in a while -- as with "Around the World in Eighty Days" or "Separate Tables," for which he won an Academy Award -- he got lucky.

He was grateful for all of it, good jobs and bad, the money, the pretty girls. In England, he had been a career army officer (he went home to serve in World War II); in New York, he'd tried to sell bootleg whiskey. Hollywood was a lot more fun.

But Sheridan Morley wants to bare the "darker, more complex and intriguing figure behind the clenched mask of the grin and tonic man," and his book seems to me heavy-handed, something David Niven was not, as his delightful autobiographies "The Moon's a Balloon" and "Bring on the Empty Horses" attest.

Determined to ferret out dark secrets, Morley offers us these revelations:

Niven had an affair with Merle Oberon, but was too gentlemanly to name her in his memoirs.

When Morley checked out some of Niven's stories, he found they had been lifted from other people.

So what? Niven told them better.

Morley characterizes Niven's career as "undistinguished and unstructured," and he is patronizing about Niven's writing. He says "show business-oriented" critics made allowances for the prose style of "The Moon's a Balloon."

In my opinion, Niven's prose style was light years ahead of Morley's. But since David Niven was the most self-mocking fabulist ever to sell 5 million copies of an autobiography, it scarcely seems necessary to try to puncture his "Balloon." Again, he did it better himself.

Most of the stories in Niven's books are told again in Morley's, but this time they don't make us laugh out loud. I remember Niven writing about the first time he went to call on Fred Astaire. Niven was fresh from a tennis game, and when Mrs. Astaire opened the front door, she reeled back, crying, "Fwed, Fwed, come quickly, there's a dwedful half-naked man out here."

In Morley's book, this is rendered as, "Fred, come quickly. There's a perfectly dreadful, half-naked man in the garden smelling horrible."

About Niven's difficulties with William Wyler, the temperamental director of "Wuthering Heights," Morley writes that Niven had signed for the role "only to have his first day on the set deafened by Wyler's increasingly hysterical attempts to get him to give a reasonable performance."

Here is Niven, in "The Moon's a Balloon," recalling that same day with Wyler:

"I glanced nervously at the instructions in my script: 'Edgar breaks down at foot of bed and sobs.'

" 'Willie,' I whispered, 'I can't do that.'

" 'Do what?'

" 'Sob. I don't know how to.'

" 'Speak up.'

" 'I don't know how to sob, Willie.'

" 'Speak up . . . louder.'

" 'I DON'T KNOW HOW TO SOB,' I yelled.

"Wyler addressed the whole set: 'Well, you've all heard it. Here's an actor who says he doesn't know how to act . . . Now . . . SOB.' "

Better, right?

Having said this, I should also say that Morley has diligently researched his subject and come up with stories from many of Niven's friends, relatives and acquaintances.

Niven appears to have believed that he had not only a talent, but also a responsibility, to amuse, and once, when a costar, Anthony Quayle, asked how he could stay so "abominably cheerful," he answered, "Well, old bean, I think that life is . . . so bloody awful that if you've got any energy at all then it's your absolute duty to try and be chirpy and keep people lively and amused and happy."

Director Blake Edwards tells Morley that Niven was a man "who always had his light bulb on: he always took a lot of trouble to shine . . ."

David Niven Jr. reports that his father led him onto the set of "Casino Royale," where there were "a lot of nude girls in a bath, because he said he wanted me to understand how arduous an actor's life could be."

Niven was not a man who had escaped sorrow. His adored first wife died in an accident -- she fell down a flight of stairs -- and at the end of his own life, he suffered from amyotrophic lateral sclerosis, sometimes called Lou Gehrig's disease.

Even as his muscles failed him, he tried to "be chirpy" about the infirmity. ("My right arm," he told the playwright John Mortimer, "has now gone over to the enemy.")

"He was a funny man and a brave man and a good man," Cary Grant said, "and there were never too many of those around here."

These reminiscences are wonderful, but when Morley rewrites, woodenly, what Niven wrote in quicksilver, you miss the original.