In general, the prelude to Dune lacks the depth of the original series. The characters seem recycled as if the authors were just filling out old templates they created. The plot suffers from the fact that the reader knows where the story ends. As for the themes, for me, the main series was most interesting with the sami-philosophical aspect of Leto II sacrificing himself for the greater good (the golden path). So, the themes and questions in prelude are minuscule and petty compared to those in the original series.
Having said all of that, I think the prelude to Dune series was an enjoyable yet shallow read. I give it 3.5 stars.