I have tried a variety of methods for learning Spanish and this one was by far better than others (with a reservation that I cover shortly).
His method starts with verbs, which I strongly prefer. He covers the words most common with English, and so he teaches the most amount in the shortest time.
He also asks for a lot of repetitions, which you are supposed say the Spanish words and sentences after the native speakers. Surprisingly, this was never boring or repetitive for me (I don't know how he did it).
This book is titled for kids. Yet, I don't see much difference between this one and his other book "Learn Spanish with Paul Noble" (except that he teaches backpack and video games as well as other concepts + he uses informal verb forms). He also has another book "Spanish Conversation with Paul Noble", although I strongly recommend you to go through these two basic ones before advancing to that one.
Now, this is where I am skeptical: I had the impression that my progress was really good with this book and I was learning Spanish very fast. I keep the possibility that maybe the book is giving me the illusion of learning Spanish. Maybe the reminder of sentences next to each other is implicitly helping me remember the words better and keep me happy, which in reality I should work harder.
All in all, I really enjoyed this book (and the other two I am currently working on). I strongly recommend you try it if you want to learn Spanish (I am not sure about the quality of his other languages, although I wouldn't be surprised if they are as good).