Almost anything by Ray Bradbury is worth a read. I never quite recovered from reading Fahrenheit 451 when I was a boy—it's about a time in the future when the government has banned books and firemen have the job of finding books in people's houses and burning them. (The title refers to the temperature at which book paper begins to burn.) Bradbury has written a lot of short stories (which I like because I don't have much of an attention span). I really enjoyed The Golden Apples of the Sun, The Martian Chronicles, and The Illustrated Man.
The Bradbury novel brings to mind three other dystopian novels: Brave New World, by Aldous Huxley, and Animal Farm and 1984 by George Orwell. All written in the 1930s and 1940s, and all predicting a dire future.
On a lighter note, you should consider digging into both the Harry Potter series and the Lord of the Rings series. (OK—"lighter" refers to the mood of the writing, not the physical weight. Both sets are somewhere near 15 to 20 pounds.) If you have seen the movies before reading the books, you will be amazed at the amount of extra detail you get. If 1500 pages at a clip seems like too much, the original J.R.R. Tolkien tale, The Hobbit, would be a good choice. It's not huge and epic like the movies; it's a simple tale originally told for the author's children. Good shade tree reading.