You may have already seen it in your iBooks app: the High Sierra update (v1.2) for my PR3 book finally cleared. There was a broken hyperlink in the book somewhere and that confused the automated verification system. Support was very helpful in helping me figure out the problem and fix it!
You can learn more about the High Sierra changes for PR3 and the ‘Packaging’ book in this post.
If you have already bought the book, you can check the ‘Updates’ section in iBooks to get it. Or you can go buy the book!