No experience with either reactive or functional programming is needed to follow the book. Familiarity with the basics of Java is required.
The content of this book is meant to be read from start to finish. It is bigger than your average tutorial and smaller than an actual book. It begins with the basics and every subsequent chapter introduces increasingly advanced features and concepts. Sections of the book are intended to be self-containing and to-the-point, so that the book can be referred back to by non-beginners.
The examples used in the book are also available in compilable java files in two formats: