On May 24, 1763, the young James Boswell called on Samuel Johnson for the first time. Boswell had long been in awe of Johnson, but this did not blunt his shrewd and rather fastidious powers of observation.

He received me very courteously; but, it must be confessed, that his apartment, and furniture, and morning dress, were sufficiently uncouth. His brown suit of clothes looked very rusty; he had on a little old shrivelled unpowdered wig, which was too small for his head; his shirt-neck and knees of his breeches were loose; his black worsted stockings ill drawn up; and he had a pair of unbuckled shoes by way of slippers. But all these slovenly particulars were forgotten the moment that he began to talk.

In all important respects, Boswell was, in Henry James’s phrase, “one upon whom nothing is lost.” Though he came to know Johnson late in the latter’s life and though his own irrepressible and pushy nature often obscured his judgment, Boswell proved the consummate biographer. In his pages “Dictionary Johnson,” flawed but magisterial, springs robustly to life in all his sloppiness and his grandeur.

Boswell was close to his subject in a way most biographers cannot be, and such proximity is usually a disadvantage. A successful biography depends upon some equipoise between intimate factual knowledge and the dispassion of distance. Boswell succeeded, not only because of his literary genius but also, I suspect, because he found himself resisting Samuel Johnson even as he was most mesmerized by him; and perhaps, too, because in some subtle way he came to view Johnson as the creation of his own stubborn Scottish brain.

It might seem unfair to begin a review of the poet and novelist Vikram Seth’s remarkable new biography by reference to the greatest of all English “lives.” But he has set himself a task of comparable difficulty, and has even compounded the difficulty: In “Two Lives” (HarperCollins, 512 pages, $27.95), Mr. Seth attempts what he calls “a double biography, an intertwined meditation, where the author is an anomalous third braid, sometimes visible, sometimes not.”

The two lives in question are those of Mr. Seth’s aunt and uncle, Henny Gerda Caro and Shanti Behari Seth. Shanti Uncle, as his nephew called him, was born in 1908 in the village of Biswan in northern India; Aunty Henny was born in the same year but a world away, into an assimilated family of German Jews in Berlin. The story of their eventual meeting and later marriage, and of their long years together in London, provides the thrust of the narrative. But coursing into this improbable and altogether astonishing tale are all manner of tributary tales, including the author’s own. Because the account covers the years from 1908 to 1998, when Shanti Uncle dies, the lives follow the terrible trajectory of the 20th century as well, from the waning days of the Raj through both World Wars and the Holocaust down to the very edge of the millennium.

Shanti Seth left India to study dentistry in Europe, ending up in Berlin, without knowing a word of German, just before the Nazi rise to power. Overcoming all manner of academic hurdles (such as having to pass a Latin exam after only six months of study), he took his qualifying degrees. In Berlin, he came within the orbit of the Caro family and especially of Henny and her sister Lola. Though Shanti was clearly enamored of Henny, she was unofficially engaged to a German; it was only many years later, in 1951, long after Henny had fled the Nazi regime and the war had ended, that the two were married. Both suffered inconsolable losses during the war. Shanti had his right arm blown off and almost died; he later learned to practice as a dentist using his left arm, though this caused him daily pain. Henny’s mother and sister Lola were rounded up and deported by the Nazis; her mother died in Theresienstadt, Lola in Auschwitz.

Such bare-bones summarization can hardly do justice to the richness of Mr. Seth’s account. He seems to have every letter or document his aunt and uncle ever wrote, together with snapshots, passports, transcripts, postcards, and other records and mementos. Especially interesting are the photos Mr. Seth has assembled, showing Aunty Henny and Shanti Uncle at almost every stage of their lives, as well as their families and many friends, Indian, German, and English. In these grainy black-and-white surfaces, the intertwined stories take on enhanced dimensions. The illustrations alone make his book a precious compendium in which the submerged history of the past century discloses the hidden faces of ordinary people caught unexpectedly in the flash of horrific events.

Even so, and despite the enormous intrinsic interest of these interlaced lives, there remains something curiously inert and perfunctory about the book. Mr. Seth cultivates such a circumspect and deferential tone throughout that his protagonists appear oddly muffled; their letters, whether written in English or translated from German, have a stilted effect. By quoting from them so copiously, and often reproducing them in facsimile, Mr. Seth works to let his aunt and uncle and all their myriad correspondents speak as characters might in a novel, but it doesn’t really work. The timid hand of deference inhibits his account.

The author is even coy with regard to himself. He marks various stages in his career merely by noting that in this year he studied Chinese or in that year his verse-novel “The Golden Gate” was in progress or later, that “A Suitable Boy” was published, but of Mr. Seth’s inner life while all these milestones were reached, we learn virtually nothing. This is frustrating because we sense that these achievements were accompanied by strong gusts of what Frost called “inner weather,” but we are left with a resume rather than a revelation.

Mr. Seth is a fine novelist and a clever poet; the book would have benefited from him bringing his skills at characterization more boldly into the biography. Instead, he not only cocoons poor Shanti Uncle and Aunty Henny in such voluminous wrappings of record that they barely breathe, he also feels impelled to inject his own capsule histories of the Third Reich or well-meaning but predictable reflections on the Arab-Israeli conflict, among many other topics, into the account. What might have been a brief but moving narrative on two unlikely destinies has instead become a lumbering, well-padded behemoth in whose ponderous paw prints the reader toils.

Had Mr. Seth conceived this book as a novel, how vibrantly it might have rung! Kipling’s well-worn lines, “East is East and West is West, and never the twain shall meet,” have never been so definitively refuted as by the protagonists of this strangely muted family romance. The passion seems to have been all on Shanti Uncle’s part, the tough practicality on Aunty Henny’s, but it’s hard to tell. In a rare moment of speculation, Mr. Seth says of Aunty Henny, “it could be that deep-seated and intense love was not in her nature, and therefore not something she could particularly empathize with,” and yet, this is as far as he will go. Accordingly his various characters remain figures in a family album; under the stiff outmoded frocks and superannuated postures a mischievous twinkle may appear or a sly smile emerge, but these are left for the reader to make of what he will. Mr. Seth proves too dutiful a biographer; he might have taken a cue from Boswell, who juggled solemn awe and saucy irreverence with equal aplomb.

eormsby@nysun.com