The link given in the 'Resources: Flat Earth Literature' topic for
Zetetic Cosmogeny no longer leads to a readable version of the book. However, a scanned copy of the original text is available for download in a variety of formats (including PDF) at the Internet Archive:
http://www.archive.org/details/zeteticcosmogon00recgoogI was also able to order a hard copy from thebookdepository.co.uk, but that appears to be the only copy they had. However, a quick google reveals you can pick up the same edition from a number of online sellers, including Amazon:
http://www.amazon.ca/Zetetic-Cosmogony-Rectangle/dp/0217959105Unfortunately, that's not just a filler-image - the cover really does look like that =/