[marcusverus]

The page links to a pdf version[0], which can easily be converted to epub using Calibre[0], which is free and open-source.

[0] https://www.gutenberg.org/ebooks/33283

[1] https://calibre-ebook.com/

[xcjs]

I'm familiar with those tools, but they don't preserve the formatting of the source document (when PDF) and certain types of embedded resources don't transfer properly.

Some PDF documents don't contain the source text as digitized text, either. It's just a bundle of scanned images.