Depends what they're interested in really, if they hate detective stories, there really isn't any point in recommending Sherlock Holmes. I've always found the Susan Cooper Dark is Rising series a good read for 'kinda creepy, kinda mystery, kinda general' interest, while if they like sci-fi, maybe the Hitchhikers Guide 'trilogy'. Hell, give them the English translation of the Guyver chapters, so they can directly compare how the sentence structure differs if you have any in their first language.
Maybe don't make him/her feel singled out, they might feel a little picked on, how about trying to get together some kind of informal book group, so a few people can read the same book, and they can talk about it, then if there's anything they have difficulty understanding in the book, they can ask about it without feeling embarrassed.