I'm not quite finished it yet, but I'm currently reading Dune by Frank Herbert. I imagine a plot synopsis would be easy enough to find on the internet so I won't bother saying what it's about because I know I won't do it justice. Basically think of it as science fictions LOTR. The book manages to create a very deep, well thought out world, without seeming overwhelming with it's history and culture which really made it easy for me to get into it and stay hooked. I also think that the pacing is just about perfect. It doesn't take long to get going, and never seems to drag on like some books can. It's always pushing the story forward which helps me stay interested.

In the event you've seen the movie before, I would recommend not basing any opinion of the book on that, because the movie didn't do it justice at all. There was a three part mini series a few years back though that was every bit as brilliant as the book if you ask me, so if you've seen it, it's a good indicator of whether or not you'll like the book. I should also point out that there are, I believe, 6 books in the series. I'm not even through the first yet and I've already bought the next two.