I liked the idea of this book: a mix of hands on Arduino builds with a kid friendly storyline. Caveat: I've only read through this myself, not yet with our kids. Overall, it was a worthwhile read and I'm looking forward to reading through it with my kids.
There was some compromise in both the story and the electronics build sections to successfully merge them together, but both were both usable. I would have picked some different builds, perhaps more that built on each other. Some later ones get reasonably complicated quickly.
The kits for the book seem to no longer be available. We won't build all of the projects, but will definitely do some of simpler ones.