Simply put, there are many people who are neither "beginners" nor "advanced". There is a section of the book titled Audience which reads > Bayes Rules! brings

Simply put, there are many people who are neither "beginners" nor "advanced". There is a section of the book titled Audience which reads > Bayes Rules! brings the power of Bayes to advanced undergraduate students and comparably trained practitioners. Accordingly, the book is neither written at the graduate level nor is it meant to be a first introduction to the field of statistics.