I was in the same predicament as you. I wouldn't call it a predicament now that I think about it, I really wanted to teach an after school reading class.  I originally wanted to do something like James and the Giant Peach but after looking at the text again it was obviously too hard for my students.

I asked one of my better English students to read a few pages out of Diary of a Wimpy Kid and he could read and understand from what I could tell but he said he couldn't explain things back to me without using Korean.

I have to go to class now but I'll try to link the topic I had earlier.

I have no reading test suggestions. 

You might want to take a look at the Dragonbreath books by Ursula Vernon if your kids end up testing around a grade 4/5 level.  They mix the usual text with comic-style pages every couple of chapters.  The books are Dragonbreath, Attack of the Ninja Frogs, Curse of the Were-Weiner, and Lair of the Bat Monster (or something similar -- it just came out). 

I was reading some information on book reports and saw Lemony Snicket's Series of Unfortunate Events ... sounds interesting. This might appeal to the death and gore in students. Also, there is a movie. 

http://www.timeforkids.com/TFK/kids/hh/writeideas/articles/0,28372,634427,00.html

The website has a good format for the students to possibly follow allong.