Two that I would add to the list are not Power BI-specific, but are both great resources for developing quality data visualizations:
The Visual Display of Quantitative Information, Edward Tufte - an absolute classic. All of Tufte’s books are worth having on your shelf.
#MakeoverMonday, Kriebel and Murray - a great exploration of the individual components that make for effective visual presentation. The authors are Tableau experts, but the book is platform-agnostic, and highly relevant for Power BI users.
- Brian