What is the humour in 'Three Men In A Boat"?

Jerome’s two main modes of humor are satire and observational humor. Satire is a mode of writing the uses irony to criticize society. It is often humorous, but does not necessarily have to be. Although some satirical novels are very dark, Jerome’s lighthearted satire is mostly concerned with illustrating and gently mocking the pretensions and hypocrisies of certain social conventions.

Observational humor sometimes overlaps with satire, especially in this case. It is a type of humor that draws its subject matter from human behavior and daily life, attempting to show the absurdity of human behavior by focusing of everyday, banal details. One example of observational humor is Jerome’s discussion of people who claim never to get seasick. The digression is meant to illustrate how most people present themselves as one type of person, in a way that's almost expected, even if they are all quite different.

In fact, the frequent use of this type of humor does provide a fairly consistent absurdist worldview. Most of Jerome's irony suggests that people are usually unaware of the extent to which they delude themselves. For instance, J.'s tone reveals that he clearly understands that he does not suffer from so many diseases, and yet he continues to progress as though it were true. Throughout the novel, Jerome revels in illustrating the illusions that men and women construct, usually fooling themselves most of all. Even though the novel remains rooted in everyday concerns, Jerome sees a regular absurdist vein that runs throughout them.