What separates Diaz's In the Distance from many other "frontier" novels

Hernan Diaz must have done a lot of research for his novel In the Distance, about a cross-country trek late-19th century (ca 1880?) by horse, covered wagon, on foot, etc. The beauty is that he wears his research lightly; this novel does not feel at all scholarly or pedantic - just leaves you wondering at every turn, how does Diaz know all this? How does he know in such detail the look and feeling of riding in a wagon train through muck and mire and desolation, crossing the salt flats on horseback, dealing with severe wounds and injuries, such as a crushed limb in need of amputation, with 19th-centruty medial implements and little to no medicines, painkillers, or sterilization? Maybe he makes it all up, summoned from his imagination - though I suspect not; I believe he build a foundation of knowledge and then "imagined" it into fiction. At times he uses a narrative technique that I am usually contemptuous of, that is, piling on topical details through sentence fragments - but Diaz makes it work, perhaps because he uses not even fragments but single words, creating long, almost poetic, screens of detail to evoke various atmospheres and conditions. Diaz is indifferent to plot - the novel, at least for the first half, involves one man's trek to reunite w/ his lost brother, though one particular twist makes this novel differ from many other frontier pieces: The protagonist, Hakan, travels from west to east, against the torrent of travelers heading west, looking for land or for gold. H boarded the wrong ship and landed in SF, and hopes to reunite w/ his brother in NYC - but faces many hardships and obstacles in his journey, each illuminating a facet of frontier life.