This book is so popular that Goodreads was able to sort through reviews and ratings submitted by their 8 and a half million members and distill them down to an infographic. It only covers the USA, but the infographic shows which states have residents who are more likely to own a copy. It also shows which states rated the title the highest.
Delaware has much to answer for. This is the one state that ranks as having both a high rating for the book as well as a higher than average rate of ownership.