Well, it's not really a 'bad' thing (I mean there is a reason why I have read every Discworld novel plus some of the others) - just that anything Rhianna writes will be compared to her fathers work and personally, in that situation, I would want to distance myself from that and create my own style.
Still, who am I to complain - you can't go wrong with more of that Pratchett style humour <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
(It's easier to criticise than create too).