One thing I learned in all of my research (and a little through experience) is that paid advertising does not work well for books.
Advertising is just that - a paid promotion. No one trusts ads! However, a review or mention will get a lot more positive attention. Press releases get better results. A magazine or newspaper feature is a big plus! Paying for a service should be the last resort for an author. We can get in front of just as many people and with far better results on our own and by using reviews & press releases.
So save your money and market more effectively!