Auguste, Duc dc Morny, adventurer, diplomat, financier, advisor to his half-brother, the Emperor Napoleon III, is today barely known in this country; this carefully researched but awkwardly assembled book tells all about him. The illegitimate son of Hortense Bonaparte, ex-queen of Holland, and of Charles de Flahaut, himself an illegitimate son of Talleyrand, Auguste, born in secrecy sometime in the fall of 1811, was brought up by Flahaut's mother, who taught him manners and gambled away his inheritance. Endowed with charm and intelligence, Auguste served in Algeria in the cavalry, was known as the King of the Paris dandies, and bestowed on himself the undeserved title, ""Comte de Morny."" First meeting his half-brother, Louis Napoleon, in 1848, he helped organize the coup d'etat of 1850, by which Napoleon made himself Emperor of France; in return Napoleon made him Minister of the Interior and President of the Chamber of Deputies. Irresistible to women, ""totally unhampered by petty bourgeois principles of morality,"" he was also a brilliant financier, a speculator and a gifted politician, serving as Ambassador to Russia. He tried, and failed, to keep Napolean from involving himself in Italy, but made the mistake of helping the Emperor establish the ill-fated French empire in Mexico in 1861-62. Given a real dukedom, he lorded it in Paris society, produced plays he claimed to have written, and died after a brief illness in 1864. Often inexact as to dates and the identity of persons named in the narrative, lacking the excitement of its era and the charm of its protagonist, this pedestrian volume is not the biography de Morny deserves. It does, however, contain little known information of value to students of the period.