This is a good book to explain tornadoes to your early elementary age children. There are good explanations of how tornadoes form, the "typical" tornado, where they most commonly occur, the classification of tornadoes, warning signs, safety measures, etc. Also, there are a few examples of specific tornadoes given. And, there are some nice photos. This is a good book to cover this topic.
As for why I rated it a 4-star instead of 5, the book just lacked that "wow factor" for me that makes a book go from good to outstanding. It also might have been nice to see a timeline for a specific tornado, or a photo progression of one specific tornado to see how they develop.