There comes a time when you’d like your Arduino to do more than just sense the environment around it, and light lights or display data on a LCD display. There comes a time when you like to move items, with motors, hydraulics, pneumatics, etc. Unless you are a mechanical engineer, you may not know how to determine the right size motor to develop the torque and hp for a particular task. I bought “Making Things Move”, and was blown away by the way the author makes concepts of force, resistance, and work simple to understand, calculate, and implement. This reference is a must have for your bookshelf or Kindle.