The book starts with Bryson explaining his curiosity about the Appalachian Trail near his house. He and his old friend Stephen Katz start hiking the trail from Georgia in the south, and stumble in the beginning with the difficulties of getting used to their equipment; Bryson also soon realizes how difficult it is to travel with his friend, who is a crude, overweight recovering alcoholic, and even less prepared for the ordeal than he is. Overburdened, they soon discard much extra food and equipment to lighten their loads.
After hiking for what seemed to him a large distance, they realize they have still barely begun while in Gatlinburg, Tennessee, and that the whole endeavor is simply too much for them. They skip a huge section of the trail, beginning again in Roanoke, Virginia. The book recounts Bryson's desire to seek easier terrain as well as "a powerful urge not to be this far south any longer". This section of the hike finally ends (after nearly 800 miles (1,300 km) of hiking) with Bryson going on a book tour and Katz returning to Des Moines, Iowa, to work.
In the following months Bryson continues to hike several smaller parts of the trail, including a visit to Centralia, Pennsylvania, the site of a coal seam fire, and eventually reunites with Katz to hike the Hundred-Mile Wilderness in Maine, which again proves too daunting. The fact that Bryson did not complete the trail is not surprising, since fewer than 25% of through-hike attempts are successful; he quotes the older figure of 10%.
At the time of his attempt to hike the Appalachian Trail, Bryson was in his forties.