What is the purpose of the descriptive detail in this passage from travels with charley?

It shows how the camper meets all the author's travel needs.

Explanation:

Travels With Charley is a travelogue written by John Steinbeck where he travels around America from his personal desire to know more about the country. Moreover, he wanted to do this out of the desire to learn more about the country his works are based on and the very source of his inspiration for these works.

The given passage from the book provides the details of what he wanted in for his travel plans. He knew he needed "a tough, fast, comfortable vehicle, mounting a camper top" which also has all the basic necessities for traveling purpose. Thus, the descriptive detail like "a little house with double bed, a four-burner stove, a heater, refrigerator and lights operating on butane, a chemical toilet, closet space, storage space, windows screened against insects" shows how the camper has all the travel needs of the author.