Greetings. On the book’s catalog page you’ll find a “Companion Content” link in the right margin:
That link takes you to the companion content’s download page, which looks like this:
The “Download the companion content” link there initiates your download of the ebook’s sample code, in this case the code that goes along with the Release Preview edition of the ebook.
PLEASE NOTE: It takes about 24 hours for the system to update the download, so at the moment the sample code for the Consumer Preview edition is still showing up here; that ZIP file is about 9 MB. The new ZIP file, which contains the code for the Release Preview edition and is about 19 MB, will begin showing up later today, I’m told, and definitely by Wednesday.
UPDATE: The correct sample code ZIP is now available, as of August 16, via the location described above.