The summary
property is intended to be used for fallback for when the server doesn't recognize the other properties of the request. Most Micropub servers understand content
and photo
, but this is a great example of an interesting content type that is likely not supported by most servers yet. In this case, summary
is the correct place for this fallback content. The content
property would be misleading since normally the content
property contains user-entered text. For example, if the user enters a note about why they wanted to read this, that could be included in the content
property.
I don't think this really solves the problem, though. If a server implementation prefers content
over summary
(which it should), with this example the context of the book title will be lost unless the server is updated to understand read-of
.