I know a thirteen year old girl who cannot read English very well, and I've been reading to her a lot. She is into romance, a genre I generally cannot stand. I got sick of reading books she chose like The Clique, so I read the Percy Jackson books to her and she loved them. She also liked Gregor the Overlander series. Anything else you can recommend based off those - you know, adventure type fifth grader level books?
Try Rick Riordan's other series, (Heroes of Olympus and The Kane Chronicles.)
The Artemis Fowl books are good :P
Try The Hunger Games. They are a little bit more advanced, I think, but they are by the same aurthor as the Gregor books.