I second (third? forth?) “A Walk in the Woods” or anything else by Bryson. He is acerbic, insightful and funny as hell. I actually avoid reading him in public, as a person sitting quietly and then suddenly GUFFAWINg does tend to cause the surprised stares of those around you.
A suggestion, though is Walt Whitman’s “Leaves of Grass”… thoughtful, metaphysical poetry, explorations of Joyful awareness, and a celebration of nature and naturality.
Regards, and happy hiking
FML
Hey, Cisco. I am located within 15 miles of the Tennessee/North Carolina border. If you plan to take a phone with you, e-mail me when you are near Asheville/ Erwin. I will be happy to meet you with some hot food. I promise to be only a little jealous of your trip. 
How about The Monkey Wrench Gang by Edward Abbey?
I re-read it on a 14-day river trip in Grand Canyon. It was obviously a perfect choice for that trip, but I can see it also being wonderful on an AT hike.
I second the Baroque cycle - a trilogy where each books is nearly 1000 pages of small type big (they’re also currently my top three all time favourite books). It would probably take you at least a month at a time to read one.
Travels In Alaska - John Muir
Wilderness - Rockwell Kent (yes, that RK)
Walking My Dog, Jane - Ned Rozell
Cradle of The Storms - Bernard Hubbard, SJ
The latter book would have to be found at an antique book dealer, but shouldn’t be expensive.
A couple more:
South - Ernest Shackleton
The Endurance - Caroline Alexander
For something thick but a great read, why not “Shogun” by James Clavell? A thousand pages of fun.
Wow, some greats recommendations here, thanks. I’ve read Shogun, Moby Dick, Into the Wild (in fact, I’ve read everything Krakauer has ever written), and A Walk in the Woods.
I’ve tried many times to listen to audio books and I can’t get through more than 10 seconds of one without zoning out and getting completely lost. I think I have undiagnosed ADD.
I and Thou, by Martin Buber (Smith translation).
Let me be one to try and dissuade you from Thoreau’s Walden. Not that it isn’t a classic, but oddly enough many find that books about nature while in nature, though seemingly a “no brainer” just don’t click when one is in the wilderness. Colin Fletcher’s The Man Who Walked Through Time has a great cover, but that’s about it. I found it an interminable bore, though his Complete Walker is practically required for an equipment and technique book prior to hitting the trail.
Interestingly enough Thoreau’s cabin was only a couple miles from downtown whereever the heck it was, he had dinner parties at his place, etc. For my part, I would lean towards tomes with a high signal to noise ratio, paperbacks are preferred by many. Light reading, non-fiction, books only tangentially related to the area you are in - wildlife/plant identification guides excepted.
I said it above, but I’ll repeat it. You probably won’t enjoy wilderness epics or weighty philosophical tomes. I highly recommend mysteries and adventure novels. That’s what everyone seems to gravitate to after a while on the trail. When you stop to read you are tired and looking to escape the realities of everyday routine.
Concord, MA.
I’ve visited and toured just about everything there is in downtown Concord.
Back in Thoreau’s day, according to the tour guides I’ve listened to, once you owned some property, you pretty much clear-cut everything around, leaving an overgrown portion as a wood lot to keep the home fires supplied.
Thoreau, one of the artsy fartsy types who were hanging around Concord at the time (along with Alcott, Hawthorne, etc.) went to Ralph Waldo Emerson and basically asked him, “Can I build a hut and live on your wood lot for a while?” He was considered quite the eccentric.
If you go to Walden Pond now, there’s a replica of Thoreau’s hut. I’ll be damned if I can figure out how he threw a dinner party in there, but I can see how the idea of trying might have caught the fancy of Thoreau’s contemporaries, the intellectual elite of Concord.
Tonight I talked with a friend who thru-hiked 2 years ago and she echoed my thoughts. Everyone sets out with the idea that their thru-hike will be a chance to expand your mind by reading the great works. The reality is that you’re too tired to deal with any complex ideas. Everyone reads very light and easy reading, and only when they have some time off. On the trail you hike all day, set up camp, cook, eat, and then go to bed.
Many folks hike with iPods and listen mostly to hard rock. They need the stimulation. Lighter music doesn’t cut it. The trail is rarely like people imagine it will be.
Don’t bother bringing books with you, or sending them to your mail drop. There’s a thriving lending library at hostels along the trail. You can pick up something many places along the way and get rid of it just as easily.
What if you really really hate the ONE book you have with you? I would sure take two at a time in case.
Just curious: why do yu think you will need something to read? There are interesting people doing the same thing there (along the trail) to talk with and you can read at home.