The overall content of the book is good. However the technical parts target the author's "ARTag" library. This library is both abandoned and proprietary. The institution that sponsored the development of the library (National Research Council of Canada) no longer funds AR work, and has taken down the SDK download. Purchasers of the book can download a single copy of the library for non-commercial use on a single computer after filling in a web form that asks for specific words from specific pages of the book. You are not permitted to redistribute the library. As far as I can tell, this is the only way to obtain the library right now, and so I cannot recommend you use it on any projects that you plan to redistribute.