The long, naughty life of Wilfrid Blunt (1840-1922)--poet, explorer, political maverick, incorrigible philanderer--should make for a great romp through the unbuttoned Victorian sub-world; and drily witty Lady Longford (Victoria R. I. ) would seem to be an ideal biographer. Odd, then, that this rich brew is only intermittently invigorating--perhaps because Longford isn't selective enough (for U. S. readers anyway), perhaps because of something un-simpatico in Blunt himself. He was a sickly, beautiful, well-born boy with a confused, fatherless, religious upbringing; he became a teenage diplomat in Europe and quickly began his career as an amorist--his second amour was famed, homey courtesan ""Skittles,"" who went on to royal beds but remained Wilfrid's chum. And once afire, Wilfrid's arranged marriage to Byron's rich granddaughter Anne did nothing to cramp his style; she stoically averted her eyes while W. S. B. capered through 40 years of overlapping liaisons, mostly with married women (e. g. Mrs. William Morris), sometimes with blatant progeny. Anne also pluckily joined W. S. B. as he, again and again, announced some ""vita nova""--bursts of spiritual or political enthusiasm: roaming unmapped Arabia; saving Arabian horsedom; losing races for Parliament. And she shared the ostracism that came with W. S. B. 's prophetic, rabid anti-imperialism--loud support for Islamic nationalisms and Irish Home Rule (he even went to prison). But, though Blunt's Islamo-philia is timely and intriguing, Longford never seems to decide how much was vision, how much a Victorian version of radical chic. And though she taps the surefire comic side of satyriasis--the sheer excess, the Feydeau foulups, the unflappable gall--she never faces what comes across as downright pathology. (Anne finally left old W. to one of his ladies, and his last ill years were spent in feuds with his miserable daughter. ) Add these fuzzinesses to the longueurs here--too much unshaped detail in the gossip and the travels--and it's a leisurely stroll through sin and politics that only Victoriana buffs will find a nonstop delight.