Dune is one of my favorite series, but I can totally see why it would be jarring. Unfortunately there are a couple of major tonal shifts throughout the series. Heck.... there's a couple just in the first book. It is definitely a very dense read. Lots going on and a lot of moving parts to track. There's even a glossary in the back to keep track of it with maps heh.
It's a really interesting universe. Herbert was really into philosophy and lead a really interesting life (his biography written by his son is an interesting read as well). It doesn't get any less dense and layered unfortunately, if that is what is keeping you out of it.
The Sci-fi mini-series was good and hit most of the major points pretty well, if you just can't deal with the books themselves. It might bring you back with some renewed interest. The new movies are interesting as a fan, but don't really tell the story fully, IMHO.