Recently, some scans by Google Books, while being in the public domain, are labeled as "Google eBook", for instance all the "digital objects" of a certain BNN series.
These books seem very hard to access: they are not returned by a Google Books search for books with preview available; clicking "ebook" brings me, after many hops including logging in, to an online reader without download option.
Finally, if I follow Google's instructions to Download & transfer books to eReaders, I have no download button at all next to the ⋮
, while I see one for other books (which ask a captcha).
So, how do I download those books? Also, if Adobe Digital Editions is required (!), why is it and what can a GNU/Linux user do?