Many people are familiar with the Lord of the rings, which became even more popular after the movie trilogy a few years ago. It's a typical saga, with novels and stories covering events on a scale of tens of thousands of years. This approach brings fanatical belonging of the readers, because studying generations of people has a huge appeal and insight into life long conflicts causes strong sentiment. The technical focus of LOTR is mostly on mythology, culture and linguistics, but sometimes it comes out too naive. People (except Frodo) are mostly black or white and most of the motives are quite superficial (and sex doesn't exist). After all, it's supposed to be a tale for children. So, in case you would like more complex stuff in your saga, you should definitely check out Dune.
Frank Herbert's Dune is a bit similar to LOTR, the whole plot (14 novels I think) extends for millenia. The story is about planet Arrakis, also known as Dune, which is the only place in the universe that produces the ultimate drug in existence, called Melange (Spice). Spice gives you higher level of conscience and prolongs life. Everybody wants and needs Spice, and the plot built around that is very complete, creative and fun to read. The whole story makes Dune a perfected alternative universe filled with complex political situations, religions, manipulation, psychology and other "adult" themes. It's freaking awesome, and it is known as one of the best sci-fi novels of all time.
The political situation of the Dune universe stands on a tripod between the emperor, noble houses and the spacing guild, which holds the monopoly on space travel. If that wasn't enough, other sources of power also exist, such as CHOAM (the biggest manufacturer of goods), the witches Bene Gesserit (with their breeding program for creating the messiah), the Tleilaxu (genetic specialists), Ixians (technology monopolists), the Mentats (human analytical computers), Swordsmen of Ginaz (superior warriors) and of course, the Fremen of Arrakis (the native people of Dune who live in sietches in the desert and tender the worms). Many players and interests - infinite possibilities of conflicts.
Another interesting thing in the novel is the flow of thought, which is solved really good. The movie (which I don't like that much, even though it's by David Lynch) tries to imitate that, but in my opinion fails quite miserably. The book does it much better, and the main mantra, used by all Bene Gesserit educated is quite inspirational:
I must not fear.
Fear is the mind-killer.
Fear is the little-death that brings total obliteration.
I will face my fear.
I will permit it to pass over me and through me.
And when it has gone past I will turn the inner eye to see its path.
Where the fear has gone there will be nothing.
Only I will remain.
Reading about prior generations of protagonists and antagonists and knowing how historical events caused the current situation makes the Dune series one of the best novels ever written. It can keep every sci-fi fan occupied for years, which is the time needed to come through the whole saga that totals in more than 5.000 pages. If you're into that sort of books, you should go for it - and then you will be able to understand why Duncan Idaho is the ultimate.