Probably, you want to understand how libraries, which are presented in the book, work. The best way to do that is to learn the background behind them — computer vision algorithms. The book provides an intuitive way of how to use computer vision libraries without spending much time on a sophisticated theory. The information provided there should be sufficient for computer vision beginners.
If you want to learn more about computer vision and image processing you should check the following course on coursera: Image and video processing: From Mars to Hollywood with a stop at the hospital. Unfortunately, it is not available now. Probably, there will be future sessions.
I highly recommend to read the book “Digital Image Processing (3rd Edition)” by Gonzalez and Woods. It covers many topics on image processing required to understand the area.
In addition, there are several good lectures on youtube, most of them assume that you have good math skills: UCF Computer Vision Video Lectures 2014
The first lecture is missing, you can find it by the following link: Lecture 01 Introduction to Computer Vision
And do not miss a book by this lecturer — Fundamentals of Computer Vision.