What is recommended books reading order offering thought leadership to read on DevOps to go from beginner to expert?
One fantastic read that offers great thought leadership on this issue and is specifically tailored to the non-technical is The Phoenix Project which is available in paperback, a Kindle E-book and as an Audiobook. This book offers an excellent starting place to educate on the who, what and why of DevOps, wich is often seen as nebulous buzzword. The official synopses states,


  Bill is an IT manager at Parts Unlimited. It's Tuesday morning and on his drive into the office, Bill gets a call from the CEO. 
  
  The company's new IT initiative, code named Phoenix Project, is critical to the future of Parts Unlimited, but the project is massively over budget and very late. The CEO wants Bill to report directly to him and fix the mess in ninety days or else Bill's entire department will be outsourced. 
  
  With the help of a prospective board member and his mysterious philosophy of The Three Ways, Bill starts to see that IT work has more in common with manufacturing plant work than he ever imagined. With the clock ticking, Bill must organize work flow streamline interdepartmental communications, and effectively serve the other business functions at Parts Unlimited.


By novelizing this story the authors are able to expertly illustrate and explain in a detailed and entertaining manner:


What DevOps means and entails
What teams and individuals are involved in DevOps
How DevOps can benefit a companies' workers and business
Challenges and weaknesses of the traditional model


While this will not explain or recommend how to do DevOps on a technical level, it will make and explain the business case and method for doing so, thereby taking you from beginner to intermediate.

The authors have also published a followup tome, the DevOps Handbook which bills itself as a how-to on "Creating World-Class Agility, Reliability, and Security in Technology Organizations," however one reviewer, FA Calkins cautioned,


  Dont buy this book if you expect it to teach you how to build a CI/CD DEVOPS environment. It is basically a review/summary of a bunch of research papers that the authors have read, but does not provide any specifics details of how to set up a CI/CD pipepline (only theory). You can get most of the content of this book by reading articles from the web. Also, you can get more specific details of how to implement CI/CD with specific tools, programs, and scripts from other sources. Dont waste your time trying to read this book if you want to deploy CI/CD. 


Though I have not yet read it (it is on my reading list!), the description claims that the book includes


  
  More than 40 DevOps case studies, including Amazon, Etsy, Capital One, Google, Facebook, Intuit, Nationwide Insurance and many more
  More than 400 pages of DevOps applications, lessons and 'how-to’s'.
  DevOps data gathered from more than 25,000 data points.
  


These resources should at least get you started on the business/philosophy piece.