BOTH OF THESE EASILY, swiftly read books will satisfy that itch in most of us to find out how the Big Rich live -- to discover if, in fact, they really are different or simply have more money. The answer seems to be, on the evidence here presented, a bit of both. True, they are of our flesh. If you prick them they bleed. But they have an inordinate ability to escape being pricked. They are vulnerable to others' greed and curiousity, but walled off by retainers. Their lives are thus more exposed and shielded, more public and more lonely than ours. They do get a lot of what they want. but God does not spare them calamities. Overall, their security infects many of them with a quickly mix of innocence and arrogance, fully demonstrated in these chronicles.

The story of the du Ponts is hard to follow, mainly because the clan was much given to procreation, to marriage among cousins, and to repeating names. There is a profusion and confusion of Eleuthere Irenees, Pierre Samuels, Alfred Victors, Lammots, Bidermanns, Henrys and Alexises. They all got their start from a powder mill founded in Delaware in 1802 by the original Pierre Samuel and his son, the first Eleuthere. But modern du Pont history begins a century later, when a weak hereditary management, representing the myriad family shareholders, was in trouble and on the verge of selling to outsiders.

At that point three young du Pont cousins raised the money to buy control from their timorous kinfolk. They were Thomas Coleman (or simply Coleman), Alfred Irenee and another Pierre Samuel.

Of the triumvirate Pierre proved to be the conquering Augustus. Only 32 years old, he led in providing the old partnership with a modern supercorporation's administrative structure. After World War I, he used the abundant profits to turn du Pont into a general chemical products combine, which later thrived unbelievably by manufacturing synthetic textiles. And he was responsible for its most spectacular feat of diversification, when it became the controlling stockholder in General Motors between 1917 and 1921. (In 1954 the U.S. government forced the separation of the two industrial giants.)

Pierre could do all this freehandedly because he bought out Coleman in 1915 and ousted Alfred from power by what Alfred saw as a dirty trick, leading to a lifelong feud. After Pierre's death in 1950 there arose none like him, and gradually du Pont heirs drifted out of managerial posts and committees until none was left. Leadership fell into the hands of board chairman Irving Shapiro, the lawyer son of a Lithuanian Jewish immigrant. One can only imagine the comment among the ghosts of du Ponts past.

The real story written by Leonard Mosley is, however, not in du Pont enterprises but in du Pont personalities. There is redheaded "General" Henry, the 19th-century autocrat of the mill. There is his sister-in-law and alleged mistress, Margaretta (or "Meta,") a mother of Medean ferocity. There are "Uncle Fred," shot to death in a whorehouse in 1893, and his brother Lammont, a brilliant and steady chemist, killed in an 1884 explosion. There are the triumvirs -- Coleman, fond of good food, good wine and bad women; thrice-married and robustly playful Alfred; finally the Augustan Pierre, a dry and frosty man, enormously competent and paternalistic but emotionally stunted, and perhaps endowed with unconscious homosexual leanings. These are but a few of a cast of what seems hundreds, fighting and fussing on every page, but also (as many current du Ponts would quickly point out) doing good works as admirals, generals, lawmakers and philanthropists.

I suspect that many of Mosley's facts are open to challenge. Not all the family papers were open to him, and he drew on cousinly hearsay, which, in the nature of things, is often both malicious and inaccurate. His business and technical material is hastily done. I find, having myself a small expertise in the General Motors story, that here at least he is decidedly sloppy. So let the reader be warned.

The Whitney story is rather more straightforward. William C. Whitney was the Yale-educated son of a middling Massachusetts businessman. He married Flora Payne, sister of a classmate, and backed by her abundant family money (which came from Standard Oil's bottomless wells) he rose to legal preeminence and fame as a Democrat in New York City. After a stint in Grover Cleveland's cabinet from 1884 to 1889, he returned from Washington to the metropolis. Entering the street railway business, he soon built his own fortune, which he spent with considerable dash.

W. A. Swanberg tells us just how: On jewels for his two wives (he was twice widowed); on Fifth Avenue mansions; on clubs and thoroughbreds; on an estate on Long Island and getaway places in South Carolina, the Adirondacks and the Berkshires, eight residences in all; on gorgeous weddings for his children; on grand tours abroad, first-class hotels, late suppers, cold bottles. He ran through it so fast that he left a mere $23 million in 1904. Swanberg does not preach, but we do get a clear realization that those Renaissance gestures, those Stanford White pleasure domes adorned with the best of Europe's past, were paid for in part by the gulled customers and stockholders of companies which Whitney and friends created, watered, milked and abandoned.

Maybe his daughter Dorothy -- younget of four children, born in 1887 -- realized that, too, for as she grew up and came into her inheritance, she put much of it into good causes of a mildly socialistic nature. And into self-education. Significantly, whereas brother Harry married a Vanderbilt, and brother Payne a Hay, and sister Pauline an English blueblood named Paget, Dorothy gave herself in wedlock in 1911 to a cerebral and "advanced" young man aptly named Willard Straight.

Straight was a Cornell graduate who dumped architecture (his major) for work in the Far East first for the Chinese government, then for ours, and finally for J.P. Morgan and Co. Soon after marrying Dorothy he came to New York to help found (with her money) The New Republic and to join an American foreign investment syndicate. He hovered between journalism and banking, uncertain of how best to pursue Higher Duties, admiring Kipling and Theodore Roosevelt and enjoying the good clubs, the servants, the travels and the other perks of wealth.

But he was charming, goodhumored, romantic and a fine descriptive writer. And doomed. Naturally, a man such as he was could not pass up the Great Crusade of 1917-18, so off to France he went as a staff officer, no doubt thinking that to die would be a very great adventure, and unaware of the script prepared by the Great Ironist. He died in bed, of influenza, three weeks after the armistice.

For Dorothy, this devastating death marked the end of an era in her life (and the world's). As Swanberg tells us in an affecting, brief, diminuendo epilogue, she continued to be a patron of The New Republic and the New School for Social Research and Cornell, and finally remarried an English educator named Elmhirst. With him and with her three children by Willard she went back to Britain (where the Whitneys originated), and to all intents vanished from the vanishing milieu of her youth. She died in 1968.

Both of these practiced popular biographers skim lightly over business and politics and thus lose chances to penetrate and freshly elucidate the connections between money and power. And both skip opportunities to comment on the clues hidden in the texture of that old, capital-S Society of pre-1917 days, moving in its cool ambience of "correct" marriages, clubs, schools, directorships, charities and retreats. Its families believed that they had a responsibility to make Wealth yield tribute to Civilization. Even their silliest extravagances were informed by a sense of rules, and that gave some significance to each of their postures. One wants to know more of how these husbands, wives, heirs and cousins went about formulating their styles, and why.

But I am only saying that there are stories here worth the attention of a Henry James or an Edith Wharton, and their possibilities are sometimes ignored in an approach that suggests a pilot script for a show to be called Upstairs, Upstairs. Nonetheless, both books are quite enjoyable for what they are.