Mastering ArduinoJson 6 Second Edition
If you never used ArduinoJson, you will appreciate this book because it guides you through your learning. It starts with the basic usage of the library and increments the complexity step by step. The last chapter analyzes several example projects and explains the design choices. It is a much better way to learn than blindly copy-pasting the examples.
If you are already using ArduinoJson, you will learn how to get the best performance and the most straightforward code. You will discover that many examples found on the Internet are suboptimal and even dangerous. The sample projects will give you a sense of how the library should be used and will give you a new perspective on your projects.