Convert unwrapped paragraphs to hard wrapped paragraphs when there's no blank lines.

[Linux for blind general discussion]

Okay, this isn't strictly an accessibility question, but I can't think
of any better place to ask and Google didn't help much.

I occasionally purchase eBooks from Smash Words as they're the only
eBook Store I know of that offers plain text along side the far too
prevalent for my liking PDF, ePub, and Kindle formats.

Problem is, their plain text eBooks are typically long enough Firefox
and Orca simply choke on them and they have paragraphs that are
unwrapped, which makes reading them with nano and SBL cumbersome.
Normally, I'd just use nano's justify command to hard wrap thewhole
file, but they lack blank lines between paragraphs, so Nano would
think the whole book a single paragraph.

So, does anyone know a way to automate inserting blank lines before
and after each line in a file that's too long to fit on the screen all
at once and then hard wrap those long lines?