HARVARD'S highbrow readers will cast the book aside after one look at the jacket. Intelligent folks just do not read Western novels, with pictures of covered wagons and cow-punchers on the outside. So Walter Van Tilburg Clark's "The Ox-Bow Incident" would get no more than a sophisticated sneer from the educated elite.

But the highbrows' loss is the hoi-polloi's gain, for inside the binding is a fascinating tale, expertly handled by a young writer who shows himself to be a master of psychological study. In addition, Clark catches the true flavor of his setting. No drug-store cowboy, the author completely revolutionizes the Zane Grey tradition of the Western novel in which men are mangled and women wangled.

"The Ox-Bow Incident" is no rippin', rarin', shootin', swearin' type of wooly Western bellowdrama, with horsemen riding hell bent for leather towards the Mexican border pursued by pop-gun posses. In Clark's book there is only one shooting and three hangings, all told, and even then the fellow that gets shot ain't killed.

The book covers a time space of slightly more than 24 hours, during which some suspected rustlers are tracked down and lynched. This is the complete action. Clark discards the traditional bombast usually associated with lynching tales, and instead creates a sombre, highly-charged situation in which every thought of individual characters is vividly represented. The action moves slowly, almost tortuously at times, because the author's emphasis is placed upon the psychological aspects of the story, rather than the external action.

Inevitably through this treatment, Clark tends to overemphasize the psychological battles within the minds of each individual in the lynching mob. He seems to endow the characters with a hesitance, a doubtfulness about the righteousness of their course which would not exist in reality. The lyncher when in white heat blazes with his hate, he does not consider in rational terms. Clark's lynchers tend to think too much.

Portrayal of the 1880 cowpuncher as a rational being gives the book a fresh touch, though by so doing, Mr. Clark runs a grave risk in departing from the conventional forms. The Old Guard, accustomed to a tradition of cowboys who were morons with all their brains in their trigger fingers, will probably call Clark's Westerners intellectual "softies." But art and the Revolution are on Mr. Clark's side.

From both psychological and stylistic angles, the book is a marked success. Clark's intense character analysis, done in narrative manner, represents a new accomplishment in the Western novel. The story unfolds in powerful fashion, marches slowly towards an inevitable moving climax, then ends on a strange dissonant note, faintly reminiscent of Stephen Crane.