Bill Bryson might not ever become the mountain man of his dreams, but he proves himself to be quite the hiker by the end of A Walk in the Woods. More importantly, however, the experience helps him come to terms with his age, his nationality, and his personal relationships. Dang. Maybe it's time for us to walk the Appalachian Trail, too?
Bryson's life is at an interesting point when we first meet him. He's recently moved back to the United States after spending most of his adulthood in England, which might explain his desire to reacquaint himself with his homeland. So it's actually an amazing coincidence that he "happened upon a path that vanished into a wood" while ambling around his house one day (1.1.1). And, yes, you guessed it—this tiny path leads directly to the Appalachian Trail.
Still, he probably didn't expect to tackle the Appalachian Trail with Stephen Katz, of all people. Although they were bros when they were younger, they now only "remained friends in a kind of theoretical sense" because their "paths had diverged wildly" (1.2.19). And to be honest, they weren't that great of friends in the first place—Katz used to drive Bryson crazy. Despite these glaring red flags, Bryson is too focused on the Appalachian Trail itself to think too much about his choice of a buddy.
Billy Boy gets quite the wake-up call when he actually begins the AT. The hike is tough from moment one, partially because Bryson hasn't gone hiking in a while, and partially because the dude is just getting old. Interestingly, however, Bryson and Katz actually get along pretty well. Sure, there are occasional moments when they beef like they're in a West Coast vs. East Coast feud, but things get along like gravy for the most part.
Eventually, Bryson realizes that it'll be impossible for them to hike the entire AT. He actually learns this in the most bummer-y way possible: he sees a four-foot map of the AT and realizes that they've only "done the bottom two inches" after several weeks of grueling hiking (1.8.15). Surprisingly, this doesn't really upset him. Instead, it frees him from the pressure of hiking the whole trail and allows him to actually enjoy the experience.
It also allows Bryson to focus on his friendship with Katz. He actually tries to hike the AT solo for a while, but find it incredibly unfulfilling (due, no doubt, to a Katz-sized hole in his heart). We see further evidence of this when Bryson freaks out over Katz' alcohol relapse. While this event certainly deserves a strong response, the fact that Bryson sees it as a "deep, foolish betrayal" of their friendship shows how much he secretly cares for Katz (2.19.144).
As you might've guessed, they never end up completing the entire trail—they don't even make it through Maine. This forces Bryson to finally admit that they "weren't boys anymore" and shouldn't be diving into such a foolhardy venture likes this (2.20.33). Like his realization that they can't hike the entire AT, however, this actually comforts Bryson, allowing him to finally feel comfortable with his place in the world. If nothing else, he'll walk away from this experience with a rekindled friendship with the kooky Stephen Katz.