At a recent workshop, I asked the participants to give me the title of their book. Some, even though they were working hard on their book, had not yet come up with a title. My advice, for brainstorming titles, is to look at books similar to yours, and search for titles similar to what you have in mind.
Among the many ways to do title research, consider worldcat.org, the world's largest library catalog. Of course you'll also punch your topic or title into Amazon and Google to see if you're in good company.
Since no one can copyright a title, there's nothing stopping you from using a book title that's already in print, but consider the need to differentiate yourself, so you're not just leading people toward another person's book.
When you do a search on Amazon or Google, your goal is not to find half a million similar terms, but to see how unique your name is. My first book Computer Ease, was a tough search because there are so many terms and titles beginning with the word "computer." I got lucky, though, with Release Your Writing, because it's the first book to show up when someone types the name in at Amazon, even if they type it without quote marks. And, at least for the time being, it comes out on top at Google too, even though there are 95,700,000 references to "release" and "writing." But the three words together make my site rise to the top.
So in considering your book's title, do your research.