The spine books used in the Visits To series, Hungry Planet and Material World, are great books for getting a glimpse of different cultures. They’re very colorful and engaging and my 9yo pulls these books off the shelf to read on his own. Window on the World is great and focuses on the religious aspect of different parts of the world, and Children Just Like Me (hands down my boys’ favorite) is easy to find very inexpensively on ebay.