There are a lot of hiking books out there, especially for the Appalachian Trail, but this book focuses on the psychological challenge a thru-hike presents. It talks about the mindset needed to complete the hike and gives you exercises (mental, not physical) to complete before and on the trail. Personally, I found this really helpful in my planning process.
And don't worry, for all you gear junkies out there... Ian of The Dusty Camel also devoted a section to this very topic. The guy is an expert after hiking the AT and the PCT and shared his vast knowledge, complete with a gear checklist.
The book is available in eReader format now and will be available in print soon. Get your booty over to Amazon.com and check it out. If you do read it, I would love to hear your thoughts on it so leave a comment or send an email.
Hope you're all having a great Monday!