This book is a survey introduction to the most important ideas in computing. It focuses on the big ideas in computer science including the major themes of recursive definitions (we can define things in terms of smaller versions of themselves), universality (programs are just another kind of data), and abstraction (hiding unnecessary details and giving things names). It covers how to describe information processes by defining procedures, how to analyze the costs required to carry out a procedure, and the fundamental limits of what can and cannot be computed mechanically.
Thanks to udacity.com, I'm now a student of Prof.Evans. I thoroughly enjoyed his teaching in the introductory CS course. "Introduction to Computing" is a different approach to computing from the usual.
I got started with this book before taking the class, and found it a bit tough to follow. But after taking couple of courses at Udacity (especially those of Prof. Evans and Prof. Wes), it all started making a lot of sense.
Highly recommended to folks in the Software Industry or Computer academics.