I agree with timdgreat, you should give it a try. Although the sex is still in some I think is not the prominent theme. And I think is a must see to learn the backgrounds of all the characters we have seen through the saga. You will get details on Duke Leto, Liet, Jessica, Baron Harkonnen, Duncan, Thuffat, Gurney, and how Shaddam gets to be Emperor. Is definitely a must read. The stories fit well in what we already have read, the prequel is supposedly frame 30 years before the story of Dune is I remember what I read in the book correctly.
So give it a try although it doesn't hurt to look for them in a library first or read excerpts of it. I buy it without a glance and can honestly say I'm not dissapointed at all.
Krystal