Recall your high school English classes, the books you had to read. Early on, it's usually Moby Dick or The Scarlet Letter or even Robinson Crusoe. Of this last, I prefer the Andy Weir version, but that's a story for a different day.
Now let's not kid ourselves. No English teacher is going to assign Tom Clancy or Danielle Steele or Nicholas Sparks. Their job is not to bump up sales at Barnes & Noble. They want culturally significant writings in the English language. A stranded sailor in the waning days of exploration, a metaphor-heavy story about an angry captain and the whale who maimed him, and religious hysteria in Colonial New England have a lot to say about how the language has evolved.
Take those three tomes with Charles Dickens' body of work, and you realize that, at least in the 18th and early 19th centuries, novelists were a wordy bunch.
And then some guy from Hannibal, Missouri writes a travelogue laced with humor, local color, and... spare prose? The Innocents Abroad is a diary of one Samuel Clemens's travels from the Mississippi River through Utah and Nevada, to California, and even to Hawaii back when it was still independent. Writing as Mark Twain, he ditches the heavy, ponderous prose of Melville and Hawthorne (and Dickens) for one-liners. Instead of long introductory essays (Hawthorne goes on a political rant about the Whigs), Twain jumps in and starts talking about preparing for his trip. This isn't fine literature. This is a cigar-chomping Border State wanderer talking to you over a bottle of whiskey.
And the eyes sweep right across the page. Even though language has shifted somewhat since 1870, you understand instinctively what Twain is saying. It's a refreshing change.
He's not the first English-language writer to cut to the chase. Shakespeare himself kept his dialog spare, lacing just enough in to avoid long passages of stage setup and sound effects. Yes, he wrote drama, but in between his less-than-subtle references to classical literature and to history (skewed, of course, toward the Tudors and their Stuart cousins) are puns, dialog meant to appeal to the masses. But Shakespeare wrote drama. Washington Irving did not. If you've ever read his essays about living among the Dutch of Upstate New York or his famous The Legend of Sleepy Hollow, you know Irving didn't waste words.
But Irving was an exception. Twain, more popular in his own time than Irving ever hoped to be, was, no pun intended, novel.
Of course, Dickens, Melville, and Hawthorne, while trying to lean into symbolism and history (sometimes contemporary history), also had to keep hungry audiences coming back. In an age before mass media, readers in Illinois or Texas had no clue about whaling ships or pre-Revolution Massachusetts. Dickens knew his readers did not just live in London, and those that did knew nothing about parts of their own city. So, internal monologue and heavy description were not just smart, they were mandatory.
Twain emerged after the Civil War, when telegraphs sent news and messages instantly across the continent. The telephone would follow in 1876. And anyone could hop the railroads and cross the country. So, people's knowledge of the world had widened. By the time of A Tramp Abroad, Twain did not have to spend pages describing the Swiss Alps or the German Black Forest unless it served his story.
In fact, the first really difficult Twain book to read is The Adventures of Huckleberry Finn, and mainly for his insistence on writing in Huck's broken dialog. On the other hand, we are discussing a book that introduces a character too racist for the Confederacy, that being Huck's Pa. The Prince and the Pauper, The Gilded Age, and Tom Sawyer all have more in common with Stephen King and Nicholas Sparks than Herman Melville.
Is it our shortening attention spans? Maybe. But Twain, for all his reputation while alive and since, was an outlier. For an example, I direct you toward Henry James's Portrait of a Lady, which begins with James doing his own literary criticism. (Spoiler alert: I abandoned that one. I could finish Moby Dick.)
It wasn't until after World War I, a few years after Twain's death, that prose started to tighten up. We now look to Hemingway as our role model. Clean, sparse prose almost to the point of white room scenes, Hemingway was part of the Lost Generation. Raymond Chandler made fun of him in a Philip Marlowe novel, but that same novel followed his example, just with more similes that fell to the ground like cocaine from a politician's coffee table. (Ouch. That was bad.)
Hemingway's time overlapped that of Tolkien, whom I would call the last of the classical writers. The Lord of the Rings trilogy has so much description, interior monologue, and side stories that Stephen King's work looks like a collection of pamphlets. But try to submit something like The Fellowship of the Ring today, and expect a form rejection letter back. Update The Old Man and the Sea for the present day, and you might get a serious look.
But I have to believe Hemingway took Twain's get-to-the-point method of storytelling as permission. Some lament the change as the death of the "high-minded novel." Normally, that means tales of middle-aged college professors in inappropriate relationships with young female students. (Actually, Philip Roth pulled that off brilliantly in The Human Stain, but that was a jumping off point.) These days, especially in crime fiction, we want our prose lean.