Hasek's novel is a combination of satire, pure comedy, social criticism, nationalistic sentiment, and pacifism. The plot is basically a series of vignettes in which the absurdity of war and social conflict are examined while a seemingly bumbling simpleton navigates his way through the eastern front of World War I.

The central character, Josef Svejk, is outwardly the "good soldier" of the title, and there is no final answer to the riddle of his behavior. The story takes place during the last days of the Austro-Hungarian Empire during the Great War. The Empire was a melange of nationalities dominated by the German-speaking Austrians. For centuries the Czechs, of whom the author was one, had been a part of Austria; with the nationalism sweeping Europe from the beginning of the nineteenth century on, the Czechs and other non-German-speaking ethnic groups wished for independence, to have their own nation states. Svejk, though a Czech from Prague, is unrealistically patriotic in favor of the Austrian cause in the war. In spite of being placed in a hospital because he is believed insane, he manages to join the army, where he has a series of mishaps and is arrested at least four times in the course of the story. Svejk is made personal servant first to an army chaplain, then to a lieutenant.

In every situation he responds to commands in a robotically dutiful way, though he is constantly mistreated, pushed around, called a fool and a numskull, and given idiotic tasks to perform such as when the chaplain sends him on a wild goose chase to obtain a huge amount of a certain special type of wine that is made only at a place kilometers away from camp. Throughout the novel it's impossible to know for sure if Svejk is really as stupid and uncomprehendingly patriotic as he seems, or if his behavior is a ruse in order to make his superiors look like fools (which they are). After he becomes the aide to Lt. Lukas, when they are on a train Svejk either pulls the emergency brake himself or tricks the conductor into doing so. The passengers, including the military men, pile out of the stopped train, then pile on when it's made ready to move again, but the upshot of the episode is that Svejk is stranded, loses his papers, and is required to purchase a new train pass though he has no money. It ends up that he is required to walk to barracks, many kilometers away in the town of Ceske Budejove (in German known as Budweis, and famous for its beer). But instead of heading south as he is supposed to, he heads west and begins a rambling journey, meeting different people who advise him to do this, or that. There is no actual explanation for why Svejk has gone in the wrong direction in the first place. One would think, as stated, that it's part of a ruse that encompasses his behavior overall, except that there is never any clear indication this is true. He eventually is arrested again, presumably for desertion, though he is also suspected of espionage. At another point he is arrested because he is wearing a Russian soldier's uniform (the Russians are the enemy) and released again. The novel ends (it was left unfinished) before Svejk can actually see combat action at the front.

The novel is thus an episodic series of comic episodes in which, though Svejk is the one constantly unlucky and being mistreated, the result is that the people in charge look even less intelligent than he is. The Austrian military command, including the chaplain, are shown as hypocrites and fools, and the nature of war, through various happenings and anecdotes related, is shown as bizarre and ridiculous. The interactions of the characters are indicative of both class conflict and the differences among the various ethnic groups that populated Austria-Hungary. On the highest level the novel is a satire on human nature in general, and the seemingly compliant and absurd behavior of Svejk is a parody of human folly, but one in which Svejk is probably hoodwinking all the "normal" people around him.