The book isn't an in-depth introduction to the low-level optimization of the API or squeezing the those graphical bytes out of the shader language. No. It's a quick-start guide! It's intended to get you up and running quickly - such as initializing the API, getting a triangle on the screen and drawing shapes (loading 3-dimensional geometry and basic shaders).
Graphical concepts by themselves could fill multiple books - effects such as shadows, reflection, lens-flare and much more. But what the book does do, is get you working with 3-dimensional geometry with your browser.
Grab a cup of Joe, lay back on your comfy sofa, and flick through - folding the odd corner page to note you must come back to that :)
Take a deep breath. and again! WebGL isn't that bad. Once you get past all the overhead code, you'll be throwing out 3d cubes and complex geometry easily - without even breaking a sweat!
Since it also runs in a browser, it means you'll be able to share your cool creations with colleagues and friends at the click of a button (just send them the link). They'll be able to run the WebGL programs on their phones, tablet or desktop. So cool! Non of this installing applications and drivers.