As far as we can understand, electron spin is the electron's intrinsic angular momentum. As far as we can tell, the electron is still regarded as a point like particle, with no internal structure and no physical size.

How can a point particle, without any physical size, spin and have intrinsic angular momentum?

The spinning of the point particle is meaningless. What matters is where the intrinsic angular momentum originates from inside the electron.

There are many people who believe that an electron's mass may have an electromagnetic origin. Is there a possibility then that the electron spin also has an electromagnetic origin? The book What Is the Electron Spin? tries to answer this question. This book is based on the assumption that the electron spin has an electromagnetic origin. That is, the electron's intrinsic angular momentum results from an electromagnetic field.

What Is the Electron Spin? makes a basic assumption that the electron itself has an electromagnetic origin. It then extends that theory to all of the electron's properties, such as mass and spin, claiming they have an electromagnetic origin as well. For example, an electron's self-energy comes from its electromagnetic field energy, and the electron spin is the angular momentum of the electron's electromagnetic field.

The first point this book attempts to make is that the electron is no longer regarded as a point particle. Rather, it purports that there is a continuum spherical distribution of both electric and magnetic charges inside the electron.

Chapter 1 is an introduction to the book and illustrates a simple electron spin model.

Chapter 2 introduces a single mathematical equation to describe how the electric charge is distributed inside the electron.

Chapter 3 introduces another mathematical equation, this one describing how the magnetic charge is distributed inside the electron.

Expanding upon the principles outlined in Chapters 2 and 3, Chapters 4 and 5 provide a solution to the electric and magnetic field distribution equations inside the electron.

Chapter 6 sets forth the notion that electron spin is the angular momentum of the electron's electromagnetic field.

Chapters 7 through 9 explain the theory that the electron's self-energy comes from its electromagnetic field energy.

Chapters 10 through 15 discuss the conservation laws surrounding electric charges, magnetic charges and electromagnetic energy.

Chapters 16 through 19 extend the electron's electromagnetic model to that of the proton, the neutron and hydrogen and helium atoms. Within these chapters, the book goes on to make the claim that it's not only an electron that has an electromagnetic origin, but all of the fundamental particles as well.

Chapters 20 through 23 of this book discuss the electromagnetic wave inside the electron. They also provide a possible solution to the hydrogen atom spectrum, setting it forth as a hydrogen atom electromagnetic stationary wave spectrum.

The last chapter, Chapter 24, discusses the symmetrical relationship between time-space and energy-momentum.

Here are some key conclusions that can be drawn from this book:

Electrons have an electromagnetic origin.

Electron spin is the electromagnetic field's angular momentum.

An electron's self-energy is a result of the electromagnetic field energy.

An electron's magnetic field is similar to that of a magnetic dipole field, where the north pole is a single unit with a negative magnetic charge and the south pole is a single unit with a positive magnetic charge.

Multiples of the electric charge unit e and the magnetic unit g equals Planck's constant h.

Protons and neutrons have an electromagnetic origin.

All materials have an electromagnetic origin.