From GameDev Academy: "We are happy to announce the launch of our free ebook Game Development for Human Beings – Build Cross-Platform Games with Phaser, authored by a highly skilled group of software engineers and game developers: Kristen Dyrr, Pablo Farias Navarro, Renan Oliveria and Ben Sparks."
GameDev Academy go on to explain how the book has 420+ pages, covering everything from basic, to advanced game development techniques using Phaser. All you need are some entry-level JavaScript skills to get started.
The book is free, and provided as a PDF.