Congrats to John Scalzi for his Hugo nomination for "Old Man's War". I hope he wins. I read a lot of science fiction including several of the other nominated books but Old Man's War was one of those instant classics, a book that 25 years from now could easily be included in a best of science fiction series. I also have to agree with Glenn Reynolds on the accesability of his work. If I wanted to get someone excited about science fiction, I would likely hand them "Enders Game", "The Foundation", and "Old Man's War"*. I just finished Vernor Vinge's "Deepness in the Sky", which was awesome. It and his previous book "Fire Upon the Deep" are beautiful and rich and deep and textured masterpieces, but I would never hand them to a SciFi first-timer. SciFi needs writers who bring the general population back to SciFi, and Scalzi along with Card and a few others will certainly help.
* Honestly, if you rank yourself as someone who hates or just doesn't read science fiction, give just one or two of these three a try. Scifi is not all cute robots and Imperial Star Destroyers. And for those looking for the next step beyond these books for more hard-core stuff I might suggest classics like "Mote in God's Eye", "Ringworld", "Dune", or about anything by Louis McMaster Bujold. After that, your ready for anything, from Charles Stross to Harlan Ellison (the latter if you want a good downer).