THE FASCINATION of war novels springs from the perennial question: what is it like? What is it like to be in combat? To know that you may be killed at any moment? To kill other human beings? To live under circumstances so extreme that most of us, no matter how often we see pictures of battle, can hardly imagine them.

Here the written word has certain advantages. Pictures show us how war looks; they may shock, dismay, and horrify; but these are the reactions of the onlooker. The participant undergoes a different experience, and his reactions are not always visible. The camera doesn't take pictures of the psyche. It can't tell us how it feels to be there.

Let A Soldier Die, William E. Holland's irst novel, sets out to do just that: to convey in depth and intensity the experience of the Bear, a helicopter gunship pilot in Vietnam. Warrant Officer Bear (a "nom de guerre") is rumpled and mustachioed by no means a model soldier, but he loves to fly choppers, the only thing he's ever done well. He's a dynamite pilot.

The flying scenes in Let a Soldier Die will make you grab hold of the arms of your chair. The risk and thrill of flight are described in absolutely convincing detail. Holland was a chopper pilot himself, and he knows how to "bump" an overloaded helicopter into the air, to fly in a nightfog, to descend inch by inch into an opening in the canopy of jugle. He knows the jargon, the flight tactics, the look and feel of a chopper's instruments, the weapons they carry -- and how to use them.

The flex guns had a sad voice. The six rotating barrels sent one bullet after another so quickly that the individual shots could not be heard . . . But the individual bullets could be distinguished. Seen from behind, a short burst was a bushel of glowing embers thrown to the wind. They fell in a long graceful arc and vanished among the trees. Hold the trigger down longer, and a long stream of red jetted forward, like water from a shaken hose. Shift the glowing dot of light in the gunsight, and the stream cold be played onto the target on which the dot fell. It was a marvelous toy.

Since flight school, the Bear has been regarded as an ace, and Holland makes the reader believe in his prowess. The only part of the job Bear dislikes is the killing. A veteran, he doesn't know whether he's killed a hundred men or two hundred. "Some pilots claim a number. I don't. I don't count them. I won't count them. But I could tell you how many men I've seen die under my guns -- I remember them all."

The lead pilot in Bear's outfit, Captain Blood, is well aware of his reluctance to fire: "He needs a special delivery telegram from God before he'll shoot." For Blood, the Vietnam war is an opportunity, and he intends to make the most of it. He has no scruples about killing. He envies the Bear because he is a better pilot, and hates him because he is a better man.

The animosity between these two is one strand of the plot in Let A Soldier Die. The inner conflict belongs to Bear alone. After firing unawares on a company of GI's, killing and wounding several, his remorse becomes almost intolerable. "Men may come to worse than dust," says one of Bear's friends, a prophecy. When Bear sees a friend go down, when the nurse who loves him is killed during the Tet shelling, when Blood prevents his transfer to a noncombat unit, the prophecy comes true.

It is to Holland's credit that Bear's experience forms a spiritual cycle. There is no pat diagnosis and no pat moral conclusions. Bear is haunted by a dream of peace and beauty which grows stronger as it grows more unattainable. Holland succeeds in presenting not merely a complex and troubled character but a complex and troubled soul.

The other characters are less fully developed. Bear's fellow pilots form a sort of wisecracking chorus, and the good nurse plays her part too conveniently. Captain Blood is as evil as his name suggests; his bloodthirstiness is all part of his obsession to advance in his Army career.

This war novel, in fact, might also be described as an Army novel. The enemy, most often seen from a safe height, is a comfortable abstraction. Blood thinks of combat missions as target practice, though the targets are sometimes living; and the war itself is a set of glorified manuvers. Questions of right and wrong, life and eath, are beside the point so long as the Army goes about its business. The paramount concern is "eficiency," the concept which measures success in terms of a body count.

In this Army, the Bear stands out as a man of principle and imagination. The Vietnam war is all to real for him, as it will be for readers of this strong first novel.