This book is a great way to introduce the world to kids. I'm not a teacher, but I'd guess it's at about a third grade reading level. The text is broken up with brightly colored pictures, so the book does not look intimidating even to a younger child. There is one map per continent, which shows climate, political boundaries, and landmarks (like major rivers and cities).
I've not followed many of the internet links yet, but I do plan to.
The most valuable parts of the book are the first two sections "What are People" and "People and Culture". These are incredibly difficult issues to address with an early elementary school student, and I feel the book does a great job. The other information in book would be possible to find elsewhere (although I doubt it would presented so beautifully), but I've found no other resource that attempts to address "What are People" at this level. The origin of humanity is not mentioned, although the word species is used, and the book states that people "belong to a group of animals called primates, which includes apes and monkeys". The wording allows for a pretty easy jump into either evolution or creationism if you want to go there, but doesn't leave you feeling like they forgot something if you just skip it all together.
Peoples of the World has the parts you'd expect from an academic work: table of contents, index, acknowledgments, even a couple of footnotes that refer you to other pages in the book. Each picture has a caption.
Another plus for the book is that if focuses on the mission of introducing young children to the beauty and diversity of the world. It does not delve into the conflicts or the horrors of the past, nor does it take sides. It avoids controversial subjects simply by stating facts. "Israel is a Jewish state which was created in 1948. Many Arabs claim that Israel's land belongs to an Arabic people, the Palestinians." is a good example of how the book gives an opening if you wish to discuss the matter, but doesn't actually go into it. It handles slavery the same way, stating when and where and who, but not delving into the subject.
I recommend this book for elementary school children. It's not overwhelming for younger children, and contains lots of starting points for older children.