This week he announced another freely available ebook, Continuous Control Techniques for Distributed Control Systems. This is the second in a series of books where the copyright has been returned to Greg after a time being held by the publisher.
Instead of burying these works in a box somewhere, Greg has chosen to make these freely available to help our current and future generations of automation and control engineers learn the craft as they search the internet and come upon these on-line works.
As he mentions in his post, this book follows in the footsteps of the first eBook, A Funny Thing Happened on the Way to the Control Room. He also mentions another eBook is planned, Biochemical Measurement and Control.