I ve just bought the ebook and was excited to try and run some pieces of the code described in the text.
It happened to be a miserable bad surprise.
The files can't be opened. Excel says something like (my message is in French so the translation is approximative)

Impossible to open "xxx.slxm" because the beta Excel version it was last saved is not supported. To open this file, save it with a supported Excel version, then retry

Heck! how can save something that is not even supported to be opened !

any clues