I don't know about this particular one, but for me I would choose a book over a class, unless the technique looks too complicated, then I might choose the class. You'll always have the book, and if you have some difficulty, you can still pick the minds of the people who took the class. But there's also the possibility that the instructor will offer a discount on her books.
You can check to see if the book is available in your local library or another nearby one. check
http://worldcat.org to see how far away the closest copy is. Then call to see if you can check it out, or request in on interlibrary loan (requires about a month or so). I saw a book where the title and front cover intrigued me, then I saw the book in the library, and it wasn't as interesting as it sounded.
There was one case where I really needed the class. I had a book on paper piecing, but I couldn't figure it out. A one evening class made it look easy.
Getting together with other people is nice, but are you paying to learn or to get together with other people?