This book is intended for developers who wish to build highly performant Qt applications for desktop and embedded devices using the C++ language. If you'd like to optimize the performance of a Qt application that has already been written, you could also find this book useful.
Furthermore, this book is aimed at intermediate-level Qt developers. While the intermediate designation is a rather broad one, we define it here as the skill level of a programmer who can implement simple Qt 5 programs using basic tooling. If you cannot do that, you should probably read an introductory Qt 5 book first.
So, let us have a look at the C++, Qt, and programming knowledge that is assumed in this book.
The Qt skills you will need include a basic knowledge of Qt Widgets, QML, and the signal-slot mechanism. You should be able to work with the Qt Creator IDE as the development environment. You should also be able to work on a Windows 10 computer.
As we will see, having a solid understanding of C++ is key to using Qt effectively. However, this book doesn't concentrate on C++ language features, so you definitively don't need to be an expert in C++ to read it.
You will, however, need to have some understanding of basic C++ features, such as object orientation, exceptions, basic templates, auto variables, and simple lambdas. Be aware that this book isn't about weird C++ language constructs, but rather tries to introduce you to a broader topic of performance, while using C++ as a sharp tool.
You also don't have to be that proficient in computer science or hardware architectures—we will always introduce the notions required as we go. The entry barrier isn't that high, so if you've already done some Qt programming in C++, you can embark on the journey.