After less than 4 weeks since the launch of the product, I've reached the $1000 mark in gross revenue!
62 copies have been sold by now and I've written about half of the book. With more than an entire month left I'm hoping to reach 100 total sales for the official (first) release.
Here are some stats:
https://pascalprecht.github.io/media/gumroad.com_dashboard_sales.png