I'm not a talented artist. In fact, I have never really done anything "good" art-wise - I'm much more of a crafter. Recently my girlfriend and I were looking to start doing colouring books or something in our spare time. I bought several colouring books from Amazon which occupy my girlfriend but I just couldn't get absorbed in them. Then, I discovered Zentangle. There are a lot of websites out there that teach you patterns etc. but none are as well put together, as easy to read or in as good of a format as this book.
I highly recommend it to artists and "normal folk" alike. It introduces a few new patterns every day, gives tips on shading and composition of your tangles and is really easy to follow. The book recommends you spend half an hour tangling a day but I spend hours doing it and completely lose track of time. However, if you only have half an hour spare then I'm sure you can get a nice pretty tile done in much less time.