The HPLIP and HPIJS user's guide is available online at:
http://hplip.sourceforge.net/

It is also available for offline reading as a Debian package, 
one just needs to install the "hplip-doc" package.  The 
documentation will then be found at /usr/share/doc/hplip-doc/,
and it will also be registered with the Debian doc-base system
so that packages like "doc-central" can find it.