If you are going with a comprehensive overview of P8, I would select Practical Poser 8.  It should give you enough basics to get you started on the right foot.  The link below will give you product comparisons, directly from SmithMicro:

http://poser.smithmicro.com/comparison.html

I am interested in a more robust app which will handle gamma correction and IDL (global illumination) in a single render without having to pad my materials with extra shader node baggage.  That is why I prefer PP 2010 over P8.  It also has queue manager which is capable of managing renders and spreading the workload over several networked computers.  And PP 2010 provides true 64 bit support.