The Microdata and RDFa also mention WebPage; the JSON-LD mushes them together.

/cc @vholland

Other issues with this Book example:

• the 'breadcrumb' property usage is goofy. Here I experiment with 'about' instead but we might want to just remove that now.

• Google testing tool complains that the review/rating data is missing info. Does it have a point?

  <script type="application/ld+json"> { "@context": "http://schema.org", "@type": "Book", "aggregateRating": { "@type": "AggregateRating", "ratingValue": "4", "reviewCount": "3077" }, "author": "/author/jd_salinger.html", "bookFormat": "http://schema.org/Paperback", "about": "Books > Literature & Fiction > Classics", "datePublished": "1991-05-01", "image": "catcher-in-the-rye-book-cover.jpg", "inLanguage": "English", "isbn": "0316769487", "name": "The Catcher in the Rye", "numberOfPages": "224", "offers": { "@type": "Offer", "availability": "http://schema.org/InStock", "price": "6.99", "priceCurrency": "USD" }, "publisher": "Little, Brown, and Company", "review": [ { "@type": "Review", "author": "John Doe", "datePublished": "2006-05-04", "name": "A masterpiece of literature", "reviewBody": "I really enjoyed this book. It captures the essential challenge people face as they try make sense of their lives and grow to adulthood.", "reviewRating": "5" }, { "@type": "Review", "author": "Bob Smith", "datePublished": "2006-06-15", "name": "A good read.", "reviewBody": "Catcher in the Rye is a fun book. It's a good book to read.", "reviewRating": "4" } ] } </script>

The exact example is here: https://github.com/schemaorg/schemaorg/blob/sdo-ganymede/data/examples.txt#L1166