I used to make jokes about 50 pound Unix Manuals. And I thoght they were jokes.. that is, until I bought "Unix: The Complete Reference".
It means business.
While not absurdly in depth, it covers all of the basics, and most of the intermediate stuff about Unix and *nix variants. It's all the stuff that a Unix Newbie needs to learn and a Weenix needs to reference. Has all the stuff about Solaris, HP-UX, BSDi and Linux, of course. Not the best reference I own, but now bad to have around. If nothing else, you can use it for a LART.
Name: Unix: The Complete Reference
Author: Kenneth Rosen, Douglas Host, James Farber, Richard Rosinski
Date Published: 1999
List Price: 39.99 USD