This book was removed, some years ago, from other digital sites because they were untrustworthy. If you buy from Glad Day, the money goes to Glad Day and me–i.e. the two noble entities who did all the work. If you find this book on another site, it’s not supposed to be there: it has been sold into book trafficking and it would very much like to come home.
This is the second edition. There’s no significant difference between the two editions, other than this one has fewer typos. (But when you Grammar Nazis find the remaining ones, please do let me know about them.)