Part I: A Voyage to Lilliput

Summary: Gulliver is shipwrecked and washes ashore in Lilliput, a land inhabited by tiny people, no more than six inches tall. He is captured and becomes a curiosity, observing their miniature society with its petty politics, absurd rituals, and fierce rivalries (like the conflict between "Big-Endians" and "Little-Endians" over how to crack an egg, satirizing religious and political schisms). Gulliver's immense size relative to the Lilliputians allows Swift to highlight the triviality and narrow-mindedness of human disputes.
Key Satire: Political corruption, religious fanaticism, human pride, the absurdity of war based on minor differences.
Part II: A Voyage to Brobdingnag

Summary: After a brief return home, Gulliver's next voyage leads him to Brobdingnag, a land populated by giants, where he is now the miniature one. He is treated as a curiosity, becoming a pet and entertainment for a giant farmer's daughter. He learns about their society, which, in contrast to Lilliput, is relatively rational and benevolent, though still prone to human flaws on a grand scale. The King of Brobdingnag, upon hearing Gulliver's descriptions of England, expresses disgust at the smallness and wickedness of European society.
Key Satire: The pettiness and moral failings of humanity seen from a superior moral perspective, the illusion of human greatness, the barbarity of European wars and politics.
Part III: A Voyage to Laputa, Balnibarbi, Luggnagg, Glubbdubdrib, and Japan

Summary: This part is a collection of shorter, interconnected voyages. Gulliver is rescued by the inhabitants of Laputa, a flying island whose people are obsessed with abstract science, mathematics, and music, but are utterly impractical and neglect their earthly affairs. He then visits Balnibarbi, the land below Laputa, where he sees the disastrous results of impractical scientific experimentation (the Academy of Lagado). He travels to Glubbdubdrib, an island of sorcerers, where he conjures historical figures and discusses history with them, exposing the fallacies and corruptions of historical accounts. Finally, he reaches Luggnagg, where he encounters the immortal but decaying Struldbrugs, who suffer from eternal old age without eternal youth, highlighting the horrors of immortality without vitality.
Key Satire: The excesses of abstract reason, the impracticality of theoretical science divorced from common sense, the corruption of history, the flawed desire for immortality.
Part IV: A Voyage to the Country of the Houyhnhnms

Summary: In the most controversial and profound part of the novel, Gulliver encounters the Houyhnhnms, a race of intelligent, rational horses, and the Yahoos, grotesque, degenerate human-like creatures who embody all the worst aspects of human nature. Gulliver gradually comes to admire the Houyhnhnms' perfect reason and virtue, and he despises the Yahoos, eventually finding it impossible to live among humans after experiencing the Houyhnhnms' pure rationality. His return to human society is deeply troubling, as he can no longer tolerate the "Yahoo-like" behavior of his fellow men.
Key Satire: The ultimate indictment of human nature, reason vs. passion, the dangers of misanthropy, the limitations of pure rationality, the moral decay of civilization.

"Gulliver's Travels" is a satirical novel published in 1726, written by Jonathan Swift. It is presented as a first-person narrative from the perspective of Lemuel Gulliver, a ship's surgeon who undertakes a series of four extraordinary voyages to fantastical and remote lands. Through Gulliver's experiences in these different societies, Swift masterfully satirizes human nature, political systems, society, morality, and the very concept of travel writing itself. Each voyage offers a critique of different aspects of European (particularly British) society, often exposing the absurdities and hypocrisies of his time. While often adapted as a children's story, the original text is a biting and complex work of social and political commentary.