Quite a few people have given this book a five or four star review (more so on the Amazon US site than the UK site).
So why am I giving it a one star review?
It seems mean to give it such a low rating as it's quite a cute little book.
However I suspect two distinct groups of reader are going to buy this book - and one of those groups should steer clear.
This book may appeal to people who want to light up LEDs but never really liked maths and have never seen a resistor.
However if you have even the most basic idea about programming - assigning values to variables and calling simple functions - and are vaguely aware of things like resistors then this book is NOT for you.
It's just too simple - there is absolutely no maths (some might say great). One formula is introduced in passing (V = IR) but is never actually used. You just build the circuits as shown - you're given the what-part but not the why-part.
So while the purpose of some parts in a given circuit are obvious, e.g. an LED that you want to switch on and off, the supporting parts, e.g. resistors, are shown but why they are needed is not explained.
Basically this is a set of recipes which you can run through quickly with a child or a very non-technically inclined person.
I bought this book as I thought it might be a good refresher on basic electronics before going onto more advanced material. But if you've seen a resistor before, even if you've forgotten everything about them and voltage and current, and done a little simple programming then you already know as much as this book will teach you.
You're better off going for the much larger Arduino Cookbook, also from O'Reilly, note that this book too can be used by people who have no knowledge of programming (this is handled in a self contained module of the book that can be skipped by those who can already program).
If the Cookbook looks a bit too hefty and dense to start with then I'd recommend The Arduino Starter Kit (lots of people are supplying different starter kits now but I mean the one actually produced by Arduino - which oddly isn't available via Amazon) - it includes a much better book that covers a set of simple introductory projects that cover way more things (and the kit includes all the parts you'll need) along with more discussion of what is going on without being scary (an adventurous child, who's already a bit interested in computers and motors etc., would have little problem with it).
This book may be a good book for a certain audience but if you're even the slightest bit geeky look elsewhere.
To be fair in the book itself it has an "Intended Audience" section where the author states "This book is written for the 'original' Arduino users: designers and artists. Therefore, it tries to explain things in a way that might drive some engineers crazy." I'd be inclined to say though that there's very little explanation full stop.