Hollaran’s World War by Tim Mahoney (Delacorte: $14.95; 224 pp.)

What’s the matter with Hollaran? Everybody wants to know, including Hollaran.

“Kind of shaky,” he explains to his boss at Jersey Sheet & Tube. “Unsure. Confused.” “Hostile and angry too,” he tells himself (but not his boss).

Also vulnerable, and, underneath the hostility, appealing. A little off-center, sure, but the kind of young man a mother wants to hug and a father wants to take to the ballgame, even though he’s 10 years too old for either.

So what’s wrong with Hollaran? He’s just back from the war, is what--a year past discharge--and with the best will in the world, he just can’t get it back together. “Holden Caulfield Returns From Nam,” or “What Happens to Good People After They Are Ordered to Do Bad Things.”

After a long hiatus--the volatile mix of pride and shame takes time to sort out--post-Vietnam books proliferate now, many of them defiant, a few of them apologetic.

Those who were not there still find it hard to understand. Most of those who were there still keep it to themselves. Tim Mahoney works both sides, opposing Hollaran, who wants desperately to get back where he was, to friend and fellow veteran Eddie Sadowski, who wants to get even.

While the rest of the world, blind to their psychic scars, just wants to get on with it, Hollaran “still can’t tell who the enemy is; could be anyone. Never know.”

Of necessity, battlefield paranoia (a VC behind every bush) has become a sixth sense with no rational outlet and with tragicomic consequences.

In his ex-wife’s house--she divorced him while he was overseas--Hollaran finds an empty six-pack of Dortmunder in the kitchen but no telltale hairs in the bed. Conclusion: “She got rid of me for some bald goddamn Kraut.” Taking a hesitant step forward, he finds a new girlfriend who longs to travel. “I’ve hardly been out of New Jersey,” she says, “except for Maine.” Conclusion: “Oh my God, she’s got some stud up in Maine. French lumberjack.”

If jobs elude Hollaran, and relationships remain tenuous, Eddie knows exactly what he wants. His entire life is devoted to constructing a diabolic machine in his basement. With it, he plans to “sandbag the bozos”--a category including just about everybody who never humped a rifle and pack around the Mekong Delta.

Asked to join Eddie’s project, Hollaran is torn between inviolable loyalty to a buddy and incipient awareness that caving in the walls is not necessarily the best way out of the cave. . . .

Set in the uncompromising grit of Newark, “Hollaran’s World War” is as swift and effective as a tracer, as illuminating as a midnight flare--a remarkable feat in view of the author’s canny reluctance to capitalize on the horrors that have warped Hollaran and woofed his buddy.

Relegation of atrocities to the recesses, though, renders them all the more effective, and infuriating.

There is anger in the book, to be sure, but an anger tempered by humor, and especially by insight.

Enough insight, in fact, to span both sides of the bozo line.