Nineteenth-century writers in the United States, whether they wrote novels, short stories, poems or plays, were powerfully drawn to the railroad in its golden years. In fact, writers responded to the railroads as soon as the first were built in the 1830's. By the 1850's, the railroad was a major presence in the life of the nation. Writers such as Ralph Waldo Emerson and Henry David saw the railroad both as a boon  to democracy  and as an object of suspicion. The railroad could be and was a despoiler  of nature, furthermore, in its manifestation of speed and noise. _ might be a despoiler of human nature as well. By the 1850's and 1860's, there was a great distrust among writer and intellectuals of the rapid industrialization of which the railroad was a leading force. Deeply philosophical historians such as Henry Adams lamented the role that the new frenzy for business was playing in eroding traditional values. A distrust of industry and business continued among writers throughout the rest of the nineteenth century and into the twentieth. For the most part, the literature in which the railroad plays and important role belong to popular culture rather than to the realm of serious art. One thinks of melodramas, boys' books, thrillers, romances, and the like rather than novels of the _ . In the railroads' prime years, between 1890 and 1920, there were a few individuals in the United States, most of them with solid railroading experience behind them, who made a profession of writing about railroading--works offering the ambience of stations, yards, and locomotive cabs. These writers, who can genuinely be said to have created a genre, the "railroad novel", are now mostly forgotten, their names having faded from memory. But anyone who takes the time to consult their fertile writings will still find a treasure trove of information about the place of the railroad in the life of the United States. According to the passage, the railroad played a significant role in literature in all of the following kinds of books except  _  .
thrillers boys' books romances important novels