I like the idea. The problem with the typical "find an informal class" advice is that many people have time they could use toward a hobby but do not have the regularity of free time to commit to a class that meets more than once, don't find the social aspects of a class desirable, or have done the informal class thing but don't know where to go from there. An informal class seems like a good way to get a sense of whether you are actually interested in the hobby but doesn't provide much real guidance. I expect writing a book like this one would involve interviewing a lot of people, though.

-sally