The book itself would probably be the best source for detailed descriptions of the different regions. It has to be available as an e-book too. Worth buying if you'd like to learn more about general cultural regions and boundaries in the US, or pirating if you don't have the funds. Just remember that even 3 decades ago it had some inaccuracies, many of which are pointed out in this thread. But it is a good primer, not very long, and a light, entertaining read, in my opinion.