Inform 7 has continued to evolve in the years since the book’s first publication. Some exciting new features have been added, but unfortunately, some syntax changes make it more difficult to follow along with the book as you’re learning the language.
If you’d like to follow along with the examples, my current recommendation is to install a legacy version of Inform which matches the source texts used in the printed book. Version 6G60 is the recommended version to use. You can find this on inform7.com by going to the Download link and then selecting that build number from the list of versions. The Errata page of this site includes changes to the book text up to this version.
Once you’re finished working your way through the book, check out the release notes for the newer version (also available on inform7.com) to see how things have improved since 2013!