Why doesn't the summary appear when using quicklook on epub formatted ebooks?

When I select an ePub formatted ebook in the Finder and then press the Space bar, a preview window opens showing a thumbnail image of the book cover, the file name, the file size and the "Last modified" date. Here is an example of an ebook containing a summary which doesn't get shown:

In the past, if an ebook contained a summary, then I would also get a summary but this is no longer the case even for ePub ebooks containing a summary.

Does anyone know how to get this feature back. I've tried various QL plugins without success and don't understand why macOS doesn't have this feature built-in.