Self help is a tool. Nothing more.
Now in reference to that, tools aren't always useful, some are poorly made and tend to break. There are also no tools that do everything, and those that try end up being combinations of other tools anyways. In reality the best toolbox someone can have has a variety of different tools, enough to do every job they require, and preferably good quality too. The tool user would also have to know how to use the tools, you wouldn't use a screw driver to tighten a nut, neither should you use a hammer to pound in a screw. Furthur still, it takes skill to use a tool and skill takes time to build.
All this applies to personal development/self help as well. Some self help is crap, other self help is excellent. Even still you need to have a variety of different techniques to use, and know when to use the right technique. Fortunately humans have two important abilities that allow us to determine these things, intuition and common sense. there are two of the most important techniques to practice as they really tap into the power of the mind and the spirit in such a way that you have greater access to being able to make correct decisions and take the correct action.
But as for the hope from the Self Help books, they are probably a crappy tool, or the wrong tool for the wrong job but don't give up on all of the tools just because they suck. Keep looking and you will find the right one. The alternative is to not look and be doomed to wallowing in the dark until something else pulls you out.
Perhaps you need to discover your purpose first?
The Meaning of Life Series How to Discover your Life Purpose in About 20 Minutes