This is based on a Nintendo game, and has had manga, an anime television show, and two movies released. The book is an easy reader illustrated with stills from the show. While the story lacks some details that would make it more understandable, the target audience for this will already know the story, so it won't seem as choppy and disjointed to them.
The target demographic for this book, second and third graders, are often very attune to trends, and certain things can become hot items very quickly. I seem to remember Battlebots, Knack Knacks, and weird versions of Legos being very popular in my own home at different points of time. Books like this are not only a good way to get children reading about things that interest them, but are good mementos to keep with the plastic gimcrackery has been sold in a garage sale.
Yo-Kai Are Real is also a great book to give to readers who older brothers and sisters may be obsessed with manga, which is not always appropriate for 8 year olds!