Goodness.. I have just finished re-reading Robinson Crusoe and Treasure Island. I don't think Miss 9 Year Old will come at either of them as they haven't stood the test of (modern) time.
Perhaps if you could find modern abridged versions?
these days are devouring Harry Potter and the action, images
and terrific vocab in them means that the old slow moving Classics are just crap to them! And crap to me too! If I hear Robinson say Woe Is Me one more time I will friggin keel
Master and Commander is a good read. She cant get all the sailing terms.. but then nor can we.. but the pace and modern structure will suit her.
I think the Hornblower series would be good.... but you MUST start her on the first of the series and do the in order. Not only was C. S. Forester writing simply but the stories are sequential. Also get her the videos of the BBC series. Ioan Gruffudd is not only an utter hunk for a 9 year old girl, the TV series kept closely to the quality of the books. His acting is quality stuff. The other cast is superb and Robert Lindsay is a standout! Being a comedic actor its a wonder he has fit so well in that series.
Don't be deceived by trantrums played out by a 9 year old... they really are quite sophisticated and need some good stuff to keep them interested. The videos will keep her interested in the books too. Master and Commander is excellent!