Mark Twain recounts the years he spent working on Mississippi River boats, first as a trainee and then as a pilot. At the time, he used his real name, Samuel Clemens. Twain got to know a diverse array of characters, as well as the river itself. Numerous aspects of the experience informed his later approach to his occupation as a writer. He also developed a lifelong appreciation of the river and of the forces of nature more generally. The book contextualizes those years with his altered perspective two decades later, when the now-experienced writer makes a return voyage as a passenger.

Twain spends the first few chapters establishing the river as a strong presence in the narrative. His attention to natural history and the river’s changing course helps the reader understand how significant the Mississippi has been in United States history. Its movements alter the boundaries of states, not just over long periods of time but sometimes overnight. The phenomenon of the “cut-off” means that the river can “jump” as it cuts throw a narrow neck of land, resulting in a straighter, shorter course.

A cut-off plays havoc with boundary lines and jurisdictions: for instance, a man is living in the State of Mississippi to-day, a cut-off occurs to-night, and to-morrow the man finds himself and his land over on the other side of the river, within the boundaries and subject to the laws of the State of Louisiana! Such a thing, happening in the upper river in the old times, could have transferred a slave from Missouri to Illinois and made a free man of him.

One of the most moving sections of the book points up the dangers that crew and passengers faced. Not only might a boat run aground or sink because it hit an underwater obstacle, but the steam engines could fail. Twain’s younger brother, Henry, trained to be a pilot at the same time he did, but Twain went on the A. C. Lacey while Henry joined a different vessel, the Pennsylvania. The night before they parted company at New Orleans, they sat up speaking about “steamboat disasters,” not suspecting that one would soon befall Henry. Two days later, when the Lacey followed, Twain learned in Mississippi that the Pennsylvania had blown up, with 150 people killed.

The wood being nearly all out of the flat now, Ealer [the pilot] rang to “come ahead” full steam, and the next moment four of the eight boilers exploded with a thunderous crash, and the whole forward third of the boat was hoisted toward the sky! The main part of the mass, with the chimneys, dropped upon the boat again, a mountain of riddled and chaotic rubbish—and then, after a little, fire broke out.

At first, Twain thought his brother had escaped, but he soon learned that Henry had died. He was blown off the boat in the explosion but was well enough to swim to shore. He perished because he decided to stay and help others. By the time the survivors were found, he was too ill to be saved.

Along with such somber events, Twain’s customary humor and love of tall tales permeate the narrative. More than twenty years later, on his return voyage, Twain attempts to travel in disguise, but it does not take long before he is exposed; chapter 24 is titled “My Incognito Is Exploded.” Pretending that he knows nothing about steamboats, much less about piloting, he listens to the boat’s captain make up lie after lie, obviously enjoying his game of fooling the ignorant traveler. As the pilot misidentifies each item...