The appendices of Dune go into more detail about Kynes and his project to reclaim the desert.
I found that bit extremely interesting. I wish they he could have gone into a bit more detail with Kynes and his efforts though.
I'm about 100 pages into 'God Emperor' perhaps it's too early to say this, but I think this might be my favorite book since the original. Leto II is such a fascinating character, at first I wanted to hate him because Sabina does, but I just can't bring myself to do it. I also am curious to see how the newest Duncan fares and how he fits into the overall story.
Without spoiling, what are your opinions on Heretics and Chapterhouse? I've read varying opinions around the web, many of them negative.