Interesting books to gain knowledge for a new reader?

I just turned 20 years old (how odd it feels saying that) and I'm seriously contemplating spending more time reading to benefit myself. I'm ashamed to say this, but the truth is I've never craved reading books of any particular subject. When I see a large book, I feel overwhelmed rather than excited. I guess some will consider me bright as I earn straight A's in university, but I'm interested in obtaining eclectic knowledge that one doesn't come across in school. In addition, I'm envious and intimidating by people who can talk such a great deal about certain books. I want to train myself to read to better myself versus because I feel forced to. I've been reading about Ayn Rand on websites and her philosophy appeals to me greatly. I'm thinking of purchasing some of her books as a start for my collection. Besides philosophy, I would like to learn about physics (as seen as Through the Wormhole), astronomy (why oh why was this never taught at my school?), and anything else that would feed my mind. I aspire to be someone of vast knowledge about the world. Perhaps there's also magazines I can subscribe to as 'light reading'? Does anyone have any recommendations?