Thinking of the kind of thing I liked or would have liked around that age...

Chronicles of Narnia
Redwall
Charles Dickens
Dorothy Sayers
Anne McCaffrey's original two Pern series. There is a little adult content in them, as there is in Dickens and Sayers, though more discreetly so in Dickens and Sayers, probably because of the eras in which they were written.

Don't forget to check out the book thread by age, elsewhere in this RResources forum.

...pronounced like the long vowel and first letter of the alphabet...