I have a learning disability, and usually the books which I understand well are quite advanced (so there's stages I have to fill in elsewhere), or they assume that you're a small child (or need to be treated like one. Even my 4-y-o daughter finds some of them patronising. This book, like only a few other music books in existance, fills that happy space in between.
I have been learning to play things for three years now, so was relieved to see that there wasn't too much detailed theory at the VERY basic level (as happens a lot). It was also assumed that adults would be learning to play, and he never once tried to patronise you.
If you want to learn some really good things quickly (I only got my mandolin for Christmas and am already quite a way through), this is the book for you. If you like lots of theory, this book may not have enough to satisfy you and you should go for something else.
Remember, this book is aimed at adults so may be a bit too complicated for someone younger