I bought this for my 10 year old daughter, who loves elephants. The pictures by Steve Bloom are breathtakingly superb, and include both African and Asian elephants.
The text, by David Henry Wilson, is really well put together. There is just enough to give the essential facts in an interesting way, without making the amount seem daunting to the younger reader. My daughter loved it, and within an hour was able to describe the differences between an African and an Asian elephant, the key features of an elephant foot, what an elephant tail is like etc... I'd say that the text was accessible to children of at least 7 and up, but would be equally accessible to younger children who had progressed beyond Oxford Reading Tree Level 4.
It's very educational - there were some facts that were new to me, about the use of elephants in Hindu festivals, and how they are decorated for the festivals (the pictures of this are amazing!).
I'm so glad we bought this, it is a great reference book for children, and I would highly recommend it. Pictures are a great way of getting children, and adults, interested - and coupled with the well designed text, this is one of the best wildlife books I've come across for primary aged children.