This discussion…
https://discussions.apple.com/thread/38 ... 0&tstart=0
… gives some idea about how one might go about converting an ibooks file to a PDF file, but it does not sound easy or likely to result in a very satisfactory viewing experience.
As to why the the Frow book on Edison cylinder machines is not available… one, Mr. Baumbach has a few "hurt copies" for sale on the Mulholland Press site and two, Mr. Baumbach might not have rights to issue that book in a different format, since, after all, he did not write the cylinder machine book.
I would like the Columbia book myself, but I'm not inclined to purchase an ipad for that purpose, at least not in the near future.
Best wishes, Mark