Life on the Mississippi was not written to be one self-contained novel from beginning to end. It is a series of anecdotes, presenting a variety of incidents and the learning experiences of a young man eager striving to attain the knowledge that will allow him to become a successful steamboat pilot.
The book begins with a history of the Mississippi River which sets the stage and makes obvious Twain's deep love of and respect for the river. Most of the first half of the book records the trials and triumphs experienced while learning about the river, the steamboat, and how to make a living on both. The second half of the book is written from the viewpoint of an experienced pilot returning to the Mississippi, observing changes in the river and in the boats traveling on it, and regretting some of the ways in which time changes all good things.