Here’s some data. Cheryl Burgess wrote a review of my book in her blog at bluefocusmarketing.com.
In the graph, you can see the change in Amazon sales ranking for the book.
Notes: To get better data, use web analytics instead of Amazon’s data. Duplicate a landing page as a single-purpose page (e.g., andreas.com/june18.html) for the blog and Tweeter posting. This lets you see where the traffic came from, the number of visitors, and number of actions.
To see who Cheryl is and why her blog can produce such results, go to the bottom of her blog page and read about her.