Here's a question that is asked in almost every seminar or workshop I teach:
Q: I have a book title I want to preserve but the book is a good ways from being ready. Is there a way to copyright a title long before the book is published? --James
A: You cannot copyright a title (or an idea) at all. You can only copyright a work. Even if you copyright a book or article with a given title, that does not prevent someone from using that title for another work, even on the same topic. Of course, none of your written material in an article or book can be used.
Once your book is published, you can (and should) register the the title with Books in Print, but again, that does not prevent someone else from using the same title, although it may discourage use.
Focus on writing your book and don't worry about "saving" the title. No one else can write your book, only you!