Try reading some of the children's classics, like Wizard of Oz, Peter Pan, Wind in the Willows, or things like that. If you want to study a few American English dialects, you could try Huckleberry Finn. Just be aware that it is considered "bad" English, with the grammatical errors one often finds in dialectic speech. You could also look for English translations of books you enjoyed as a child, like Grimm's Fairy Tales.

I have developed a deep appreciation for the classics in the past year or so, but would recommend against most of /u/Jakava's list if you are pressed for time. Many of those books can't be properly digested unless you take your time with them. A couple could be downright confusing to someone quickly reading them in a non-native tongue.