Zentangle Basics by Suzanne McNeill has remained my favourite even though I own four other related book. She starts from the beginning listing the few materials that you need to get started and what ages this art form would be appropriate, ages five and up. Very quickly, Suzanne gets you started with your first drawing. She shows step by step illustrations of how to draw each tangle, both as a full square of each and then as part of a mulit-tangle drawing. In all she show 24 step by step tangles.
One of the best features of the book, are the images of completed tangles drawn using the illustrated tangles. She also gives lots of ideas of how and where to use Zentangles in your daily activities.
No matter that I own several other Zentangle books, this is the one that I keep coming back to time and again. I highly recommend Zentangle Basics for anyone wanting to start this type of drawing. This book is widely available from most book retailers and even from some quilt shops and art stores.