I really enjoyed the Heresy series, yes there are some jarring writer transitions but to me those just showcase the different Legions. The Cain archives are pretty good too but to me the best are the Eisenhorn and Ravenor books. Love em.

As for the rulebook, I did not notice too many changes in the fluff (emperor is still dieing, deamon-poo keeps hitting the intergalactic fan) apart from some seriously creepy new artwork for the dark eldar.

One thing stood out though: Squats are back! Go read appendix I, the bit about abhumans.