This book attempts to fill the need for good information about mechanical design. The book starts out with a whirlwind tour of various fundamental measures, calculations, and mechanical concepts, such as force, mass, acceleration, etc. He manages to present this information in a reasonable format and at a reasonable pace. While you won't end up being a physics major by reading the first couple of sections, it does provide a solid basis for the discussions found later in the book. Overall, it is a concise and practical explaination of the basics, focusing on the things you need to know.
Subsequent sections are all well written, concise, and focus on concepts that are easy to grasp.
I found all of the material to be good practical knowledge for anyone building an electro-mechanical device. He does a good job describing how motors work, and various ways of controlling them and measuring their characteristics. A good explaination of stepper motors is also included. Other sections include gears, pulleys, springs, hydraulics, pneumatics, and a variety of other useful topics. Each topic explains enough to get you going on your own design.