The Appalachian Trail is a a 2200 mile(3500km) trail running from Georgia to Maine in the Eastern United States. The only book I used for the entire trail was Wingfoot’s Thru-hikers handbook. It has all the data you need: water sources, shelters, towns and the services the towns offer, and the mileages between them. I brought the entire book, minus the cover, and ripped out and threw away the pages as I used them. The whole book, I think, weighed 7-9 oz(226grams). I ripped out the days page and kept it in a small plastic ziplock in my pocket and the rest of the book was kept in a gallon size ziplock in my pack. The trail is very well marked with white blazes painted on the trees. I didn’t need any maps or any other guide book.
I came to the trail with enough water to get me to the next water source and enough food to get me to the next food source. That’s how I hiked the whole trail and it worked great. I found that buying my food along the way gave me more freedom. I didn’t have to wait for my packages in towns or stop at towns that I didn’t want to stop at. I would usually buy food every 3 days or so. For one stretch in New York there was some source of calories every day. Sometimes I would hike out of town with a whole pizza wrapped up in foil in my food bag. Town food has a lot more power to it then a box of old dry food that you send yourself.
To prepare for the AT I would suggest reading Beyond Backpacking: Ray Jardines Guide to Lightweight Hiking and getting your pack weight down. My base weight ( all my stuff minus food, water, and fuel) was 11-12lbs(5kg) and probably never weighed more then 25lbs(11kg) fully loaded with food, water and fuel. My load included a tent with full bug and rain protection, a warm sleeping bag and a good stove. I had everything I needed; that’s important, don’t go so light that you don’t have the gear you need to take care of yourself. So many times I have put the rain poncho shelter, the 1lb sleeping bag, and the 13oz backpack on my gear list only to be hit with the reality that the pack hurts my shoulders, I get wet in the tarp and the 1lb sleeping bag is too cold.
For foot wear I wore Chaco Z/1 Sandals for the entire trail. I wore socks with them and when it got snowy or cold I wore them with neoprene socks. In the snow my feet were cold and uncomfortable, but they survived. Buy the right size for your foot and don’t worry about stubbing your toe. I have hiked over 4000 miles (6400km) in sandals and though my toes go right up to the end, I have never stubbed them.
I also read books by people that had hiked the trail and read online journals about people who had hiked it. It helps to kind of know what to expect.