At the risk of insulting your intelligence, try the following two
commands:

  man man
  man apropos


...of course, man-pages aren't perfect.  They have a fundamental bias of
assuming that you know broadly where lies the answer to your question
(though apropos helps make that a little less severe).  But, they are
extensive and invaluable.

Beyond that, there's the Web pages.

More?  I'm not aware of any English NetBSD-specific books in print (but
there are occasional stirrings of people talking about writing them, or
talking about talking about writing them...).  However, NetBSD is a member
of a large family of operating systems (including the general BSD clan).  
From the NetBSD homepage, there is a list of recommended books on various
topics; if you just want reliable information, you can get a good
apprximation from that list.  (^&  If you also want to ``vote with your
wallet'' and throw money at authors/publishers that support NetBSD...

Well, you could donate to the NetBSD foundation, or you could pester
publishers about when they will produce a NetBSD book on some topic...(^&

(If you find any NetBSD-specific books not listed on the NetBSD
recommended reading list, you might let people know...)


(Hm.  Publishers to watch for...you know, in an odd sort of way, Dover
somehow seems like a good ideological match for a NetBSD book.  (^&)


  "I probably don't know what I'm talking about."  --rkr@rkr.kcnet.com