WordPress Web Application Development - Second Edition 2nd ed. Edition

This book is awesome. It walks through building a web application on top of WordPress. I tried a few other books that I thought covered the same topic. This one was by far the best I have read on using WordPress as a web application. I actually came back to Amazon to order the print version because I want a paper copy for reference (I previously bought the kindle version).

This book covers web app development using WordPress, anything from theme structure to advanced custom post types to working with APIs on the front end. The book shows that WordPress is way more than simple blogging platform or CMS, it can be used as a backend or platform to build web applications.