It seemed somehow symbolic of the fashionable Second Empire,"" wrote one of its fashionable members, ""that for the first time in history a dentist had succeeded in achieving an establishment comparable only [to that] of a prince."" The dentist was Dr. Thomas W. Evans (1823-1897), of humble West Philadelphia, official surgeon-dentist to Napoleon III and a choice subject for a historian of cultural byways. Carson (The Social History of Bourbon, The Polite Americans, The Golden Egg) doesn't attempt a conventional biography; rather, ha intersperses aspects of Evans' protean life with vignettes of the Bonapartes and matches of period-color. We hear about Evans' boyhood bent for dentistry, the contemporary state of the art (American professionalism vs. French charlatanism), and Evans' lifetime contributions to it. We see young Evans, ambitious (as ha put it) for ""celebrity, position, and fortune,"" arrive to assist a French practitioner; then, induce his first royal patient, Bavaria's King Ludwig, to meet him halfway; later, travel in a single week ""from Sandringham to St. Petersburg."" (""At Stockholm Evans would check the teeth of King Oscar's sons, with a final stop at Berlin to visit his special friend, Queen Augusta."") Twice, as Carson notes, ha entered mainstream history--as a staunch Unionist (with Napoleon's car) in pro-Confederate Paris, and through his daring rescue of the beauteous, suddenly-friendless Eugenie at the fall of the Second Empire--to Evans, the apogee of his career. The reader, however, may blink more at Evans' other accomplishments. As an insider with an eye for real-estate values, he made his fortune during Haussmann's rebuilding of Paris (his own hÃ´tel arose on the Avenue Foch-to-be). Impressed by the Sanitary Commission's tare of wounded Civil War soldiers, ha went to the Crimea, pressed for reforms in military hygiene (""and the contribution that a private, voluntary organization could make""), and, during the Franco-Prussian War, set up Paris' most effective ""Ambulance""--actually, an unprecedented field hospital under canvas. He also had, as his official mistress of three decades, one of the era's great demimondaines, Marie Laurent--beloved of Manet and MallarmÃ‰. Carson has mounted this intriguing personage with a delicacy and restraint that enhances, rather than exhausts, his interest.