The digital version of the 4th edition of the Math Guide is available now from the Google Play store in every country where Google Play sells books. I will have an announcement about the paperback version soon.
(One thing that’s not done on the Google Play book is the cover. I’m working with someone to update the cover from the old design I’ve used for the last two editions. A cover is so unimportant for a digital book, though, that I didn’t want to delay the release just for that reason.)