THE LAST third of the 19th century has been conveniently relegated to the dark recesses of the collective memory, perceived, if at all, as a murky period in the American experience that served as an unremarkable bridge between the stillness at Appomattox and the 20th century. The perception is wrong, although understandable, as it was a time of shattered illusions, flickering idealism, social Darwinism and rampant greed. Gould . . . Tweed . . . Fisk . . . trusts . . . an arguably rigged presidential election. Hardly the stuff of which memorable Fourth of July oratory is made. Or, with rare exception, memorable historical fiction.

Thomas Fleming's The Spoils of War is one of those welcome exceptions. Fleming has pulled a host of skeletons out of the historical closet, brought them to life, fleshed them out, dressed them in the glittering finery and tawdry mores of the times, and interwoven them with highly credible fictional characters. The result is an ambitious, perceptive and, on balance, absorbing saga of a colorful and chaotic chapter in American history.

At the fictional center are Jonathan Stapleton, widower, millionaire, Civil War general, treasurer of the Republican Party, senator; his Louisiana-bred second wife, Cynthia Legrand Stapleton, the widow of Jonathan's dead brother Charles (who perished in the 1850s during an abortive scheme to wrest Cuba from Spain), who must play second fiddle to Jonathan's political obsessions; Jonathan's mercurial, morally flawed son, Rawdon (the spitting image of his dead Uncle Charlie), who has the Right Schools (St. Paul's, Princeton) but not the Right Stuff -- an "angel of darkness who spoke in the cadences of light"; Rawdon's gifted wife, Genevieve Dall Stapleton, whose journalistic talents and social vision are belittled by her insecure husband and stunted by the macho mindset of the times; and Rawdon's Princeton classmate, the South Carolinian Clay Pendleton, "an ex-mama's boy who only wanted to be a survivor," whose principles and promising newspaper career are sucked into the vortex of William Randolph Hearst's yellow journalism.

These Stapletons move in an opulent circle of Vanderbilts, Astors and Roosevelts, and a bevy of unbridled capitalists who make money the >real old-fashioned way -- they steal it.

The moral drift troubles Jonathan Stapleton, a Lincoln Republican who sees his country and his party slipping away from the bright promise of Appomattox, abhors the machinations of the financier Jay Gould, whose gold market cornering scheme had led to the financial ruin and suicide of Jonathan's closest friend, but uses Gould money to rearrange the unpalatable outcome of the 1876 presidential election. Jonathan is a principled fixer bent on preserving his Republic(ans) at any cost. Others are remarkably untroubled by the casual amorality of the times. Fleming's Gould takes the fix in stride and pointedly reminds Jonathan: "I didn't give you . . . a million dollars just to put this Ohio chucklehead in the White House. I expect a healthy return on all my investments."

The moral drift even envelops Jonathan's son Rawdon. The young idealist who once reached for the stars now reaches for the jugular. Rawdon sides with Gould against his father; takes Genevieve's widowed, monied younger sister as his mistress, driving Genevieve to a breakdown and a sanitarium; squanders fortunes; then retreats to Cuba to fan the flames of a revolution he envisions as a prelude to the empire tht had eluded his Uncle Charlie 40 years before.

FLEMING skillfuly moves his story from Wall Street to the New York City newsrooms of Pultizer and Hearst, to Gould's yacht, Egypt, Spain and, finally, to the revolutionary tinderbox of Cuba, where a recovered and resilient Genevieve and a disillusioned and embittered Clay Pendleton, now Hearst employes, feverishly churn out incendiary journalistic fiction under a bemused Rawdon's watchful eye, and the battleship Maine sits silently, invitingly, in Havana harbor.

Fleming brings this absorbing mix of fact and fiction off with considerable skill, and few lapses. The opening chapters move a bit slowly. Some historical figures do not so much participate as intrude -- as when Harriet Beecher Stowe appears in one of Genevieve's dreams to declare: "No one's ever going to swoon over you." And there's a gratuitous escapade where young Rawdon and his Princeton mates spend an evening at a brothel, the details of which might best be left to a Harold Robbins anthology.

These are minor defects in a polished and perceptive account of imperfect men and women making their way in an imperfect society whose moral compass is fixed on Wall Street, and whose only rule is that there are no rules.

In the closing pages of this book, Genevieve Dall Stapleton, amidst the carnage of a military hospital in Cuba, tells the author Stephen Crane, "I'm not a novelist."

Thomas Fleming is -- and a good one.