This book is about a new and very radical information-theoretic approach to comprehending and modelling reality. It is called Process Physics because it uses a process model of time rather than, as in current physics, a non-process geometrical model of time, a model so successfully developed and used by Galileo, Newton, Einstein and others that for many physicists the phenomenon of time is actually identified with this geometrical model. Now, for the first time in the history of physics, we have a model of time that includes the distinctions between past, present and future. These distinctions cannot be made in the geometrical model of time. For this reason we can call the current prevailing physics Non-Process Physics. In Process Physics we turn to a fundamental reformulation of the key concepts in physics. This entails that we must identify both the successes and failures of the Non-Process Physics, for it almost succeeded.