I wouldn't call A new Earth just "self-development stuff" because its not a method of Eckhartt Tolle but the access to the natural conciousness for the now.
None of this self-development stuff helps without clearing out the crap, no matter what you read or who you talk to, none of it will sink in unless you leave room for it to grow.
I don't know exactly what you mean but A new Earth does make you grow. It shows you the very broad and tricky "mechanics" of the ego. Its doesn't make anything than giving you awareness about your ego. And awareness is the most important part of releasing something. If you have the awareness for example if you see a woman and you instantly feel uncomfortable, that feeling has to dissappear because the light of conciousness falls on it, the light of the now where all thoughts and thought related feelings can't exist.
My experience: Lets take the same example again, the woman that makes you feel uncomfortable. As you are aware the first time the feeling doesn't really disappear or if, only for some seconds and then the ego comes back. But the more you are aware about your ego, the longer those states of natural conciousness get, the more your mental problems are fading because they can't exist in the now where you are basically completely happy.
Your ego then fights for its place and you are even more aware about it because it comes up with much bigger thoughts. Like you have not social sexuality thoughts (I want to bang her) for several months and then the "desperate" ego throws in such a thought again.