I came across this quite by accident when browsing in an arts and crafts store several weeks ago. I ordered it and bought a small journal, pen and pencil and eagerly awaited the book arrival. It's simply beautiful. It's great for beginner tanglers, but I can understand if some people find the options overwhelming. The art examples presented as examples of what you can create with the patterns are visually stunning.
The authors present the information in sections: introduction to art, the principles of Zentangle, and the supplies required, the actual patterns (over 100), then ends with other artistic things you can do with Zentangle.
The only small problem I have with the book, even though I love it, is that I wish some of the patterns showed a few more steps to illustrate how to make the pattern. Not many, just a few, and I realize that could just be a result of my beginner status.
I have noticed an increased creativity and desire to be more artistic, creative in problem-solving and more calm (though I am usually a very calm person). I haven't really noticed increased focus, but that could come with further practice.
Overall, a fantastic introduction to the craft.