Forget a
Walk In the Woods. Bill Bryson is a punk who used hearsay and lores for monetary advantage. I read the book years ago because it was recommended to me, his stories seemed a bit wild then and I have since realized an overweight scholar with his imaginary friend "Katz" has no decent story about the AT, only whining and embellishment. /Rant.
If you are looking for a book to read before hand, grab
AWOL on the Appalachian Trail by David Miller, or
Barefoot Sisters, Southbound by Lucy and Susan Letcher. Both written by well established thru-hikers.
I would not recommend the Data Book to carry. It is a slimmed down version of the
Thru-Hikers Companion. I would strongly recommend picking up the Companion for your planning. It has all the information you need for the trail. Do your research and planning with the Companion, take notes, and leave it at home. You can also download the Companion in PDF form.
http://www.aldha.org/comp_pdf.htm
For your book to carry, get
The AT Guide. It is very well organized with your elevation map on every page. It is fantastic to see your shelters, water, and other important information in a visual form that you can see the difficulty of the trail ahead of you.
http://www.theatguide.com/
The last bit of paper is a topographical map. This comes in for an even better idea of your day ahead of you, as well as safety. You should never need a topographical map, as you should never leave the Trail unless you are planning a round trip using side trails, but it's something you don't want to be caught without. I use mine almost every stop, to compare against the guide book.
Whiteblaze.net has a wealth of information for you about everything from planning/preparing, food, trail info, gear, more than you could imagine.
My best advice I can give to you is prepare, plan, train, repeat. Start hiking every day you can increasing to a full pack weight, and the shoes you will be wearing. Your muscles and more importantly joints need to get used to carrying that extra weight. If you drop that on yourself all at once, you will get injured, and you will be miserable. The trail is not a place to get in shape.
Gear- Is it absolutely necessary to carry? "No", "not really", "well if...", "but": Don't bring it! The lighter your pack, the happier your hike. No big knife or hatchet needed. Shakedowns are a lot of fun with new hikers, you dump out their bag, sort into 4 categories, and start tossing items in a box they don't need. Your first shakedown will amaze you with the difference in your next hike. I started with a 23lb dry pack, well under most everyone, and still lost 5lbs on my first shakedown. At the same time, you do need to make sure that you have the essentials for your safety and comfort. Investing in the right clothes and sleep system makes a big difference. Don't be the guy other people have to take care of, because you wore cotton or didn't bring a tent expecting to have shelter space every night.
Hiking on the AT for 5 miles or 2,000 is a blast. It was a life changing experience to me. Time and effort spent now will come back to you tripled on your trip(s). I can help you a whole lot more, always feel free to ask questions. If I can find it I will send you a packing list I built for some friends, I think it's on this hard drive.