The book may not be available; if it was available, the posts may have expired. If there are copyright issues, the name of the book might have been obsfucated. Different news providers have different levels of retention. If it is available, it's likely yenc'ed and/or rar'ed. Rar is the compression method of choice for most binary newsgroups.
Almost all international newsgroups in the principle newsgroup hierarchies (alt., comp., and so on) default to English.
Many newservers only keep a certain posts online for a limited amount of time (it's called "retention" in news-speek).
Depending on what newsgroups you visit, you may find them awash in trolls, spammers, and malware; over the years, I have seen several newsgroups go to hell and be abandoned by legitimate users. Usenet has many wild and woolly neighborhoods and back alleys.
I use Giganews and have used it with satisfaction for years; it has excellent retention (we're talking years), but a subscription costs money (several tiers of subscription are available).
Their FAQ might answer some of your questions. http://www.giganews.com/support/usenet/#usenet
Wikipedia has a very good article on Usenet. http://en.wikipedia.org/wiki/Usenet