The work of Walter Russell (1871-1963) is known to relatively few people, and hardly understood or appreciated in today's 'scientific' world.
For an introduction to the person, see his wiki page but also the nice booklet by Glenn Clark 'The man who tapped the secrets of the universe'. I recommend to read this concise but inspiring booklet to gain an appreciation of Russell as a special person and true polymath: he was not just the author of a unified theory of physics and cosmogony but also a painter, sculptor, philosopher, etc.
In 1926 Russell wrote his first major work 'The Universal One' after a period of visionary enlightenment or intuitive insight. He refers to this special experience of ‘illumination’ that happened in 1921, but also the fact it’s almost impossible to find words to describe it afterwards.
The book, and his work in general, is not exactly easy to read. Writing style and terminology, but also his particular scientific approach are rather demanding: one has to be willing and able to read over and through all this and study - intuitively beyond purely intellectual - in order to grasp the theoretical framework that he lays out.
In a later phase of his life he also wrote ‘The Secret of Light’ (1947) and ‘A New Concept of the Universe’ (1953), as well as a ‘Home Study Course’ in the same period (1950-52).
Note that although Russell refined his language and descriptions over the decades, the framework he lays out is overall very consistent. To ease the entry, several people have written introductions and notes to the work of Walter Russell. (see  below)