Its Great to see all the great suggestions.
Does it make me more of a geek that I know a lot of them, and while not having read all of them, am mostly familiar with most.
One thing I have to admit is that while they are all great books, I often don't refer many of them to newbies as they are heavy getting into.
Case in point J.R.R. Tolkein - Lord of the Rings. While I personally love the books, and love the Movie's even more, it took me 4 or 5 attempts before I could get through the whole story without just giving up. I actually ended up finishing it in one night after watching The Fellowship of the Ring the first time
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Similarly, I stopped recommending Robert Jordan's Wheel of Time series after it started being extended and extended. I'll probably wait till the final part, based on his notes finally comes out.