WITH THE UNITED STATES embroiled in a seemingly endless military conflict marked by shifting goals, evolving justifications, and ever-rising death tolls, Denis Johnson's portrayal of a senseless war and its casualties, Tree of Smoke (Farrar, Straus and Giroux, $27), couldn't be timelier. Johnson earned a place in the exclusive pantheon of "writers' writers" with his 1992 short-story collection Jesus' Son, a pitch-perfect portrayal of the surreal lives of America's drifters and junkies. In Tree of Smoke, his first novel in nine years, he continues to traffic in the dispossessed, but this time he draws in characters from around the world and sets them adrift in the streets and jungles of Vietnam, circa 1963, where people are constantly coming and going "on murky errands." We watch as Colonel Francis Sands, a WWII hero and psy-ops agent "held upright by the power of his own history," struggles with the moral ambiguity of his latest assignment; Kathy Jones, a humanitarian worker and Seventh-Day Adventist, watches her religious convictions dissolve into loneliness; James Houston, a troubled teenager in a U.S. Army recon unit, trades the romantic ethos of the Wild West for the less burdensome law of the jungle; and Trung Than, a Vietcong revolutionary, weighs the perils of idealism against the security of the status quo as he struggles with the temptation of betrayal. In gorgeous prose that weaves between clarity and hallucinatory opaqueness, Johnson tracks his characters through 20 years of life at home and abroad, from the heady times of the Kennedy era to the nihilism of Reagan's eighties. Though bound together by no more than fleeting coincidences, their stories create a heartbreaking portrait of war as each comes to the perspective held by a young CIA agent who follows a harrowing string of disasters to his own demise: "He'd come to war to see abstractions become realities. Instead he'd seen the reverse. Everything was abstract now."