My 6 year old was asked to use this by his teacher, and it certainly seems to be a simple logical method to start learning piano and reading music.
It's a biggy. Amazon supplied the US version which means the names of the notes are US names not English names, which is very frustrating for the adults and confusing for the child. I've gone through the book changing each instance, but I wouldn't recommend buying this book through Amazon unless they clarify that it's the UK version that you'll be getting. The teacher says this has happened before, so mine wasn't just a rogue batch.