There are several OpenCV C++ books in the market, this one is Python version. I am really glad that someone wrote a book describing how to implement computer vision algorithms using Python.
One of the most difficult part in OpenCV is how to install the library. This book starts with highly detailed installation instructions for Linux, Windows and Mac OS. The author shows readers different I/O operations, such as reading/writing image, video files and accessing cameras. The book also discusses the much needed GUI utilities and APIs. One of the very useful section in the book is how to train haar cascade features in xml files.