[Jellby]

Originally Posted by Adjust

I've seen some with this OPF reference.

<metadata xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:opf="http://www.idpf.org/2007/opf">

I don't know what this means or why it's needed.

It defines a namespace. It means you can use attributes from the OPF specification by prefixing them with "opf:" (see below).

<dc:creator>Author Name</dc:creator>

Also why this line needs to be changed to below?

<dc:creator opf:role="aut" opf:file-as="Name, Author">Author Name</dc:creator>

The "role" and "file-as" attributes come from the OPF spec, that's why they have the "opf:" prefix, as defined above. The "role" attribute says that "Author Name" is the author of the book (it could have been the illustrator, the editor, the illustrator, the compilator...). The "file-as" attribute gives a standardized form to sort the author, something like the "author_sort" in calibre, if you use it. It's not strictly needed, but it's nice to have, although it's ignored by many (most?) readers.

What's the best way to format the Blurb? Is it ok to keep it all on one long line, inserting breaks only at paragraphs, or can I insert line breaks to condense the width?

I've found that a single line per paragraph works best, otherwise the inserted line breaks can appear as forced line breaks.