As far as sequels go, Dune Messiah is excellent. Not as in depth as the original, only because the first book did an outstanding job of world-building. The main characters, especially Paul and Alia, have matured, and they way in which they cope with their prescience is intriguing. My only complaints are that Lady Jessica was not involved in any meaningful way, and there weren't any frightening Sandworm encounters. Hoping both make an appearance in the next book.