Very cool resource.

Have you thought about adding the scale of the author's following and/or social media presence?

For example, this story's author has 21,000 followers on Twitter, and a successful blog.

Another example is 200k in sales https://news.ycombinator.com/item?id=23502770 where the self-publishing author admitted that practically all sales were due to 35,000 Twitter followers.

Have you come across an example of a successful book launch where an (unknown) author didn't already have a large following?