I have not read this from cover to cover. However, this was my main spiritual reading for about a year. What I would do is look in the index and go to chapters that dealt with whatever I was going through. His counsel on dealing with anxiety I remember to have been especially good.
So, in short, even if you don't want to read it all, this is a great one to keep on your shelf. You never know when you might need sound advice on a specific topic.