My older daughter is a prolific reader and is intellectually about 15 years old. However, she is just 9, and emotionally very much her real age - if that old, to be honest. She has very low tolerance for even mild peril, but her particular challenge is rule-breaking or naughtiness of any kind. To give an example - we had to turn off the DVD "Cloudy with a Chance of Meatballs" after about 10 minutes when one character wouldn't let another pass on the pavement! She's slightly better with written descriptions than visuals, but not much, to be honest.
She's also not into anything about boys, makeup, giggly pre-teen stuff. I also find myself clutching my pearls a bit at those themes. I have to emphasise - she's a very young 9 year old in many ways.
So far we've had success with:
- older classics - I find the language is complex enough to engage her, but the concepts and themes are 'safe'. So - The Secret Garden, Little Women that kind of thing, but also Helen Cresswell when we can find them. She actually mentioned Oliver Twist yesterday, but if I remember correctly that's a bit harrowing.
- all the Enid Blyton school stuff, plus Secret 7 and Famous 5, all a couple of years ago. I think she's left that stuff behind now.
- Percy Jackson and all variations. These are probably her favourites and have sparked a real interest in mythology of all kinds. Rick Riordan cannot write fast enough to satisfy her.
So - I'm sure I'm not the only one in this predicament. What we seem to need is challenging vocabulary used in stories with very little tension, no love interest and no antagonists! Easy right? 
We talked about Artemis Fowl last night and she's downloaded that onto her Kindle - think she'll like it? I've never read them. If anyone knows of any good myth-based stories, or non-fiction that might suit, that's be great too. Other than than, any suggestions?