Hustling colleagues, family, and friends to pen a testimonial about your book for Amazon.com isn't panning out as an effective tactic for sales. It takes plenty more than that static measure in this era of folks orbiting on the web and mobile at such high speed.
So, how to keep interest alive in your book? Have it out there as a conversation piece. And not only digitally. Give that talk at the Chamber of Commerce and issue periodic press releases. Teach a course at the community college. Word of mouth will surge.