This book has helped me more than any other in the area of organization. Granted, I don't have it down completely as life tends to knock me off my track frequently, but this book has been a tremendous help. The major premise of this book is that you must get things out of your head and into some sort of system whereby it will not be forgotten. He details a paper based system. I have set up a system based on Allen's concepts that utilizes both paper and computer. Iqtell.com is based on this system and has been a tremendous help to me.
A few months back I got a "new" desk that has cubby holes in it for papers. According to Allen's system, I set up one cubby as an inbox, another as an outbox, two are for in progress and one is for bills. His system doesn't use a separate box for bills, but a separate one for bills is a must for me, because we have so many medical bills and other bills filling up my mailbox all the time. If I kept them all in the inbox, I'm afraid they would get buried and not paid on time.
The essential thing for this book to be of any use to you is that you set up a system, similar to what he describes in the book, that works for you and that you use it. The neat thing about this system is if life throws a curve ball at you and you get derailed, it's okay because everything is right there where you left off and you can just pick up and start again. You don't have to make a whole new to-do list. It's still there and all you need to do is add to it or subtract from it.
I can't say enough about Allen's concept for getting things done. It has taken a lot of stress off for me as long as I make sure I use it. That is the key...use it. Get things in the calendar as soon as they are scheduled. Add tasks to the system as soon as you know you have a new task. Add reminders to the system as soon as you know you need to remember something. The more you get out of your head and into the system the more it relieves stress because you don't have to juggle twenty reminders in your head or on little pieces of scrap paper all over the place.