Hi thanks fot your replies. Ive read all the horus heresy books and am about to start listening to them in audio form as bought the big collection at christmas. I was looking for one or two more 40k specific books before i comitted fully.
Fire caste looks good ill go with that.
I have both lords and preists of mars but was waiting for the third one before starting.Same with Pariah waiting for all three though loooks like that could be a long wait