Put it all down. No one need see while we are alive."" So art-connoisseur Bernard Berenaon told his wife Mary some 60 years after she became his first disciple, then his collaborator, lover, defender, goad;and the quotation is, fittingly, Ernest Samuels' epigraph. Samuels, the multiple-prize-winning biographer of Henry Adams, was not exposed to Berenson's testy charm and he is not a great hand at anecdotes anyhow; but he has meticulously reconstructed, from the vast Berenson archives (BB had 1,400 correspondents!), the formative years of an illustrious, erratic, unsatisfied life. The cicerone of Italian Renaissance painting was born in a lithuanian ghetto and grew up, infatuated with books and nature, in the uncongenial North End of Boston; still in his teens, he was a guest at stately homes when his father came to the door with a pushcart--and, not to embarrass Bernard, beat a hasty retreat. Thereafter, the doubt: was his pursuit of ""perfect culture"" (a la Arnold and Pater) also a flight from ghetto origins? Harvard mentor William James gave the quest a psychological inflection (the reconstruction of a personality would be BB's lasting contribution to art history), and wealthy patrons--always a need and a nemesis--made it possible. But as the years of rapturously touting Europe stretched out, producing only a stream of letters, the ""debt of expectation"" (BB) grew--only to be discharged with the aid of the importunate Mary. Dislodged from a stifling marriage by Bernard's ardors, she traveled about with him in search of ""transcendent beauty"" and fresh attributions; and from the list of paintings they compiled and a small essay of Mary's grew his first major work, The Venetian Painters of the Renaissance (1893). Later he would blame her for turning him from philosophy and pure aesthetics to pedantry and picture-mongering, and she too had doubts. Here as elsewhere, Samuels reserves judgment; but the continuing story of the pair's ruptures and reconciliations, Bernard's growing host of acolytes, intimates, and ""enemy-friends"" (the two were connoisseurs, equally, of people), and the hotly-contested steps to Celebrity at I Tatti is, per se, of absorbing interest. One might wish that Samuels knew more about art (one painter or another, here, could as well be apples or pears), but he has retrieved Berenson from the idolators and disparagers--achievement enough.