The Melancholy of Haruhi Suzumiya. It's a light novel (around two-hundred pages) and, in the US at least, is recommended for ages fourteen-and-up. In other words everyone here will be able to breeze through it. At the same, though, it's probably the only slice-of-life story that includes references to Hyperion and advanced mathematics. I don't want to reveal too much but think of it as a deconstruction of anime in general.
...okay, too vague. Umm...if you like anime or the more lighthearted Discworld novels then you'll probably like this one.