This book is about the general limits of the universe.
Or what can or can't be done within the universe.
AKA counterfactuals.
Traditionally, when trying to explain something using physics,
you need to start with initial conditions and the laws of motion.
This is a satisfactory method when it comes to explaining where a ball
will land, but what is the initial condition of the initial condition of the universe?
What is the initial condition of knowledge?
The author believes that the laws of motion may be derivative
of something more fundamental: counterfactuals.
To explain something using counterfactuals, you don't need
initial conditions and the laws of motion.
Counterfactuals allow you to make specific laws about traditionally
approximate entities such as energy, heat, and work.
They also allow you to bring abstract-ish concepts like
knowledge and information into the sphere of physics.
Pretty cool stuff.
If for nothing else, read this book to find out the interesting connection between
work* and information.

*work-like energy transfer