Stylistically the books were somewhat different. Wool describes a dystopia of sort. I guess the situation Starship Troopers describes could be considered dystopic by some. Dune is something different altogether. It's more of an amalgam of fantasy and sci-fi. This makes it a really interesting read!
Dune and Starship Troopers operarte on a more philosophical level than Wool. Particularly Dune is a really layered and somewhat complicated book. There are many underlying themes of which I managed to understand a few properly. It probably would benefit a lot from another read.
Wool is more straight-forward than these two. It is the most story-driven of the three. It seems to me that Heinlein wrote the story of Starship Troopers just to make it possible for him to examine various themes, morality, society and citizenship included.
Movie Versions
It has been a long time since I saw the movie version by Verhoeven. It would be interesting to see the movie again with the book fresh in mind. The first time I saw that I thought it was incredibly campy. Perhaps there is some proper message beyond the camp.Apparently Lynch's made a version of Dune. There seem to be several mini-series available as well. There is definitely a lot of material to tap into. The book I read is just a starting point. I'm not sure if I want to tackle the whole series anytime soon, though.
It would not surprise me if someone made a really awesome movie or a mini-series out of Wool. I believe it would translate somewhat well to the screen. It's more straightforward than both Dune and Starship Troopers.
Conclusion
I enjoyed particularly Dune. It felt like character development could have been stronger in certain points. Certain events just didn't have the impact they could have. This is not a big flaw, though. The story more than makes up for this. Some claim Dune is the LoTR of sci-fi. I wouldn't object to that. It's a great book.
Wool describes a possible dystopia. Perhaps that's what makes it a bit scary. Howey is an excellent storyteller. I will definitely keep an eye on this series and keep on reading the parts as they are released. If you decide to read this, get the omnibus edition.
Starship Troopers was definitely an interesting read. Even though the action sequences were well written, I felt the story and characters were somewhat hollow (particularly the protagonist). Fortunately it's not a thick book. What makes it interesting is the philosophical content. It definitely makes you think.