Witnessing To Dracula book by Billy Ng.

Since the release of my book 'Witnessing To Dracula: A Memoir of Ministry in Romania', I am averaging about 300 book sales per month. My sales have mainly been to churches and online friends. I find it difficult to reach people outside of this circle of influence ie. I am unknown to most people outside New York. I am wondering whether you have the same problem and whether you have found a solution which you might be willing to share with the rest of the community. Specifically, I am asking authors who had paid for book marketing services by companies such as Ingram and Jenkins group (which range from a few hundred to many thousands of dollars) whether these type of programs work and whether it is cost effective. They promise a lot but do they deliver?