Gulliver's Travels was written in parts, separated sometimes by years. In fact, Swift wrote the fourth part of the book before he wrote the third; this out-of-order composition was corrected when the parts were gathered into one novel. The book does hold together very well, considering that it was censored and edited for content several times. Each part is connected by Gulliver's continuing need to travel and explore, and by his failure to justify English society to the other cultures that he finds. The character of Gulliver decried any attempt to alter the narrative:
...I do not remember I gave you power to consent that any thing should be omitted, and much less that any thing should be inserted; therefore, as to the latter, I do here renounce every thing of that kind...
(Swift, Gulliver's Travels, gutenberg.org)
The book was published as one work, but is often shortened to just the Lilliput section. This loses most of the satirical aspects of the story, focusing instead on the fantastic adventure aspect. Each part of the story was written specifically to focus on and satirize an aspect of real-world culture, so the book is best understood as a whole. Reading any one section of the book alone will give only the superficial adventure and satire contained in that section; by reading the whole book, the satire builds on itself from part to part, culminating in the total condemnation of English culture by Gulliver in favor of the rationalistic society of the Houyhnhnms.