I see a lot of complaints from people that they can’t find some of the Matthew Corbett books in physical book editions. As of now, all of the books are available in physical formats.
I’ve put together a page that lists online sources from which physical book editions of all of the Matthew Corbett books can be purchased. There are other places that may have some books, but I have verified that these links are valid and active as of this posting. I will try to maintain the links going forward.