CreateSpace reports I've sold 498 paperbacks since my first book was published, so that's about 180 a year or about 15 a month. Regarding Kindle, that is more difficult to estimate because of the sales and the unlimited being separate, but I'd say I sold about 50 books a month this last quarter. My books actually sell less over time however, they sold more when they were new and #1 in the JW genre.
For those not acquainted, these are my two books:
Journey to God's House: www.amazon.com/Journey-Gods-House-Headquarters-Witnesses-ebook/dp/B00EEIWUFW
Escape from Paradise: www.amazon.com/Escape-Paradise-Jehovahs-Witnesses-thirty-five-ebook/dp/B00S292JS2/
That said, those reading this should know I wrote my books to help people, not to make money. One woman recently wrote that she quit her free home Bible study because of my book, so that is very satisfying. While I'm no Ray Franz, I've tried to do my part.
Also, it should be said that I could have spent all that time writing, publishing, etc. making money at my job where one good sale would make as much as years worth of selling books. I figured this would be the case up front and wrote as a labor of love. Finally, I have given all of the money I've made so far on those books to charity.
However, I am now writing my first novel (fiction) tentatively entitled "The Redemption Sect". If I ever can finish it, and if it every makes any money, I'm keeping it!
Brock Talon