Work of irony both deplores Vietnam and lauds the military; Gardens of Stone, by Nicholas Profitt. New York: Carroll & Graf Publishers. 373 pp. $14.95.

Nicholas Profitt has good timing. What better occasion for a book extolling military men than now, with American public opinion in favor of the invasion of Grenada by United States Marines, and with the armed forces once again becoming a respectable career choice among the young.

It's hard not to feel the irony. Ten years ago, with Vietnam still splintering the nation's soul, this book would have been unsalable.And for anyone torn by the anguish of that period, it's hard to believe a book could rely heavily on Vietnam and at the same time laud the life of a military man.

That Mr. Profitt is able to carry this feat off through the portrayal of sympathetic - if idealized - characters is a measure of his skill as a writer. His story is set against the backdrop of Arlington National Cemetery. It is played out, for the most part, in the ranks of the Old Guard, an elite infantry honor guard that carries out burials at the cemetery.

It is in particular a story of two men: Jackie Willow, a young recruit raring to ship out and have a go at the Vietcong, and Sgt. Clell Hazard, a gruff ''lifer'' who loves the military but turns against the war in Vietnam.

Profitt, a former Old Guard sergeant and an ex-foreign correspondent for Newsweek, writes with an insider's swagger and affection. His work reflects the tight, lean prose of a seasoned reporter. His attention to detail brings a compelling vividness to the story, especially in a series of flash-forwards depicting the nightmare of Vietnam.

The skills that account for the strength in Profitt's writing, however, also propel the many flaws that mar this book. A reporter, by profession, is not a storyteller - he is a conveyor of facts. He thinks in terms of structure: this fact here, that quotation here - he builds, he tinkers, but essentially he does not create.

In many ways, Profitt has ''reported'' this novel. His structural devices are almost as painfully obvious as the who, what, when, where, why, of a news story. His paradoxes are almost too perfect, his characters too black and white. Profitt is masterly at getting the details right, but he misses subtleties and shadings of motives and feeling.

In developing the story's two romances, for example, he writes graphically about sex but never really taps love. In short, Profitt is good at manipulating the slick surface that is the hallmark of entertainment; regrettably, he never crosses the threshold into the complexities and depths that shape literature.

Such shortcomings aside, one could almost recommend this book for an evening or two of wry reading, were it not for Profitt's deplorable use of virtually every form of obscenity one can imagine. And one can't help feeling somewhat dismayed in considering reports the book may become a movie. Unfortunately, ''Gardens of Stone'' has all the stereotypical ingredients Hollywood too often falls for - violence, sex, action. One wishes it also had a heart to redeem it.