1. Science Fantasy done right- Like Lucas before him (yes, trust me it's a good comparison), Monte Cook has filtered the genre greats (Gene Wolfe, Jack Vance, Moebius) and come out with a superior setting, open for exploration.
2. Exploration and discovery is first - This is not a system geared primarily to fighting creatures. Yes, there will be encounters with creatures large and small that want to eat you and fighting is your only option. But sometimes, you are encountering things whose goals aren't to end your character- their existence in your general vicinity just happen to be hazardous to your health. How do you respond then? Your rewards are more tied to your discoveries. Sometimes a discovery is figuring out how to solve that scenario without fighting, and therefore getting those beings to aid you in your bigger goal. It's all about storytelling.
3. Simple mechanics that empower players and free GMs - Monte has really build a system that many have likened to being a blend between the options heavy mainstream games and the storytelling focus of the indie games and I couldn't agree more.
Check out NinthWorldHub.com and TF9W.com for a fan site and podcast that help fill in those points and give you a better picture of what playing Numenera will deliver in deep entertainment value.
-David Wilson Brown