Robert B. Parker and Louis L’Amour have more in common than a guaranteed spot on the New York Times list of bestselling writers: From the late 1970s through the first decade of the twenty-first century, they saved America’s place in world literature.

At a time when America’s eastern intelligentsia was performing last rites for the Western, L’Amour’s frontier novels finished consistently among the top five most popular books in the world. When Parker’s first Spenser novel, The Godwulf Manuscript, appeared in 1973, Ross Macdonald, the last surviving member of the trinity that included Dashiell Hammett and Raymond Chandler, was nearing the end of his Lew Archer, private detective, series—drawing the curtain, some said, on a tradition that began in 1920. Within a handful of years, Spenser would sell in the millions and drag dozens of new private eye writers into print on the broad tails of his trenchcoat.

When a juggernaut like the Western cedes much of its share of the market to competitors, the talking heads take notice and write its obituary. They overlook the fact that no other genre has ever commanded so much attention. It stood to reason, given the spread of technology, from primitive video games to Twitter, that the Western would surrender its dominance. What it has done—as opposed to the fat historical melodramas of the 1950s and nearly all of so-called mainstream fiction—is survive. In theaters, it has outlasted the comedy short, the travelogue, and the cartoon. In 100 years, not a twelvemonth has passed that  …