I will second the DK Readers - lots of illustrations together with some illuminating text.
Another one my DD8 really loved at that age was the Magic Treehouse series of books - both audio and the actual books. She was 100% engaged and absorbed an incredible amount of information - to the point where when we were watching 'Ice Age' together at around that age and I pointed out the cave paintings she was quite unfazed, just shrugged and told me that she had already been informed about them by the Magic Treehouse!
