One of the most basic things you need to know when describing your own book is what your character wants. I can't even begin to list how many times I've read this when looking up tips for query writing. What does your character want, and what stops him from getting it? That's your basic conflict, and that's all anybody really wants to know when you're summarizing your book. But here's my issue with this concept: at any point in your life, whether you're making a big decision or a little one, do you always know what you want? So what if your character doesn't know what he wants? Is your story set up for failure?
I'm still avoiding my book like the plague, but I have given it a bit more thought, and I've broken it down into three parts. I've mentioned before that I feel the third part is the weakest, and it's not just because I can't write the last chapter to save my life. I think it has something to do with the fact that my MC doesn't know what he wants. In the first two parts, he didn't exactly have everything figured out, but he at least had a good idea about what he wanted. He just had to figure out how to get it, and how much he could get. But as the story progresses and things get more complicated, what he actually wants is hard to figure out.
I don't necessarily think this is going to kill my story. Whenever you're reaching the end of a book, the characters are probably going to have to make some decisions that help wrap up the whole story and bring it to its conclusion. If your story is about a love triangle, then your MC is going to have to pick one person. If it's an epic quest, then your hero will probably have to choose whether or not to complete it even when it seems impossible. A lot of stories will have decisions being made in the final act.
This thought process has helped me feel a little better about the fact that my MC has a hard time figuring out what he wants in the final act. Where I think I went wrong was in the execution. He's very wishy-washy about it, which just doesn't fit his character at all. He also doesn't seem to realize that a choice even needs to be made until the very last minute (which is a big part of why I think my last chapter doesn't work). Maybe what he wants is just to figure out what he wants, which is ok, but it can't just dawn on him out of nowhere. He has to be constantly aware of it, which I don't think I pulled off.
So a decision may be a big part of the final chapters of your book. Even if your character knows what he wants in the beginning, things can happen throughout the story that make it harder to figure out exactly what he wants in the end. But as long as he knows a decision needs to be made, then it won't throw the reader off when he finally makes it.
Your character may not always know what he wants. It isn't the end of the world for your story. You just have to help him figure it out.