I recommend the book as a good introduction to the subject. As Garden notes in the introduction, he is writing for a general audience and he does that well. The book provides interesting information about a wide range of Nazi film. The book as a particularly good selection of images, some in color. No other book on the topic can equal it in this regard.
The author has also set up a useful web site to supplement the book.
There are a few matters of fact and interpretation about which I might quibble, but when my students ask me for help on where to start in understanding Nazi film this is the first book to which I will send them.