The primary focus of this book is the OpenGL Shading Language (GLSL). Therefore, we don't spend any time discussing the basics of programming with OpenGL. In this book I assume that the reader has some experience with programming in OpenGL, and understands 3D rendering concepts such as model coordinates, view coordinates, clip coordinates, perspective transforms, and the other associated transformations. There's no assumption of any experience with shader programming, however, so if you're new to GLSL, this is a great place to start.
If you're an OpenGL programmer looking to learn about GLSL programming, then this book is for you. Even if you have some shader programming experience, you will very likely find the recipes in this book to be valuable. We cover a range of simple to advanced techniques, using some of the latest features of OpenGL (such as compute shaders and tessellation shaders). So experienced GLSL programmers, who are looking to learn how to use these new features, may also find this book to be useful.
In short, this book is for programmers who understand the basics of 3D graphics in OpenGL, and are interested in either learning GLSL, or taking advantage of some of the newest features in modern GLSL 4.x.