A friend of mine recently asked his friends what we all thought of self-help. And because the answer was longer than could be reasonably encapsulated in a paragraph or two, I figured I'd respond here.
Self help tends to fall into one of six (by my reckoning) categories...and the different categories have different levels of effectiveness.
Category one: The self-help book that attempts to help you change your personality. Sorry, it's substantially genetic. You mostly just lose. Some books in this category admit it, for instance Sonja Ljubomirsky's Happiness book leads by saying 50% of your happiness is basically genetic and unmodifiable outside of decade-long work that no one is willing to do.
Category two: The self-help book that attempts to teach you something new. See, for instance, Robert Greene's books on Seduction or Power. I prefer Yudkowsky's term for this kind of book: Epiphany porn. She looks awful good on the pages, but she ain't gonna do you. What you think once has no impact on your life at all, with p>0.99. So what is one to do?
Category three: The books that attempt to teach you to think differently as a habit are a completely different category of book. Much academic learning tries to do this but fails. Some succeeds. This is easily understood by folks who took their curricula seriously, and studied a brain-bending discipline (I know personally that math, econ, philosophy all try to deeply reconfigure how you think about everything. In general, I found that psychology didn't...nor did most education courses). The good news is that this is far better than insight porn. It can actually change how you think about many things. The bad news is that again, it probably has no impact on your life at all (p > 0.95). Human beings suck very very badly at translating idea into action. If it involves human action in natural realms (dealing with people), 19 times out of 20, your action will remain as it was, while you think about your failure differently than you used to. WTF? So we're screwed?
Category four: The book that attempts to teach you to act differently as a habit is a kind of book that has some chance of working. I found that Neil Strauss's 2nd book on Game was a beautifully well-done book in this form. What can you do? The primary issue that self help books fail on is that self-help is 99% about action and 1% about thinking. And almost all of them attempt to screw with your thinking, not your action.
Category five: Long term books. A sequence of meditation practice books can be beautifully self-helpful, if you practice their approach over the course of decades, without seeing much progress at any one point. Good Luck.
Category six: Encouragement books. Some books exist simply to give you the psychic strength to persevere. Much fiction is like this. Neil Straus's first book on Game is like this. Gain strength from the story to persevere in building a habit. IF you use this kind of book this way, it can be useful. Most folks don't.
There are two primary issues in self-help:
1. Action is 95% of the issue...what you think matters almost not at all.
2. Habit is 99% of the issue. Anything you do once is useless.
3. Motivation is essential. Getting motivation supplements helps. Almost no one can build habitual action without motivational supplements...and stories are one such.
Books fail at at least a 99.95% rate to address the twin dangers of needing both action-focus and habit-focus, and most of them are not primarily motivational. But then again...books are about as bad a medium as one could find for getting any of these things you need for actual life changes. Talking head lecturing would be even worse.
How this impacts New Years resolutions is left as an exercise for the reader.