I bought this as a book to enhance my understanding of computing before applying to study Computer Science at University, and I find that it really did make me understand it. The book starts out at absolute first principles - lightbulbs and switches - making only very gradual advancements until before you realise it, the author has just described most of how an Altair 8080 works. If you already understand the ideas of binary numbers and other basic, non-computational stuff then you can skip a few chapters out of the beginning, while the majority of the last chapter focuses on things common to us today - e.g. graphics, sound etc - so again, most of the last chapter can be safely skimmed. On the other hand, the book does give you a real appreciation of just how much we have advanced in the years since the book's creation. No complicated terms are used in the book without prior explanation, all the time simply building on the understanding created throughout the book.
I would definitely recommend this to anyone interested in the mechanics of computing, or even to people who might not think of themselves as being particularly mathematical.