Whichever most convenient way to obtain a full restriction-free PDF of a book. Fetched one by one through various channels in my case. Very few are in the publi

Whichever most convenient way to obtain a full restriction-free PDF of a book. Fetched one by one through various channels in my case. Very few are in the public domain, if any. BTW one can do the same with academic publications, device manuals, or whatever else content available in PDF.