From my experiences in the previous books, 

Practical Poser is a tell all/be all "Here's this, here's what it does and here's how to do a few things to get you started learning" excellent book, awesome illustrations to go with it.

Poser X  Revealed is more of a text book, I actually used Poser 6 Revealed in an online class when I first started learning P6.  It's a great book, but, yeah, it's like the manual with lessons thrown in...still a good book for reference purposes, and a little more detailed then the shipped manual.

Though I like both books, I would highly recommend PP7 as a first buy.  You will probably like it better.