This four-volume work represents the most comprehensive documentation and study of the creation of general relativity; one of the fundamental physical theories of the 20th century. It contains the direct facsimile, transcript and explanation of and comments on the Einstein Zurich Notebook as written in 1912. The research by Einstein herein forms a pivotal part of his creation of the theory of General Relativity (1915) from Special Relativity (1905) and Newton's law of gravitation. Additional sources from Einstein and others who from the late 19th to the early 20th century contributed to this monumental development sources are presented here in translation for the first time. The volumes offer detailed commentaries and analyses of these sources that are based on a close reading of these documents supplemented by interpretations by the leading historians of relativity. All in all, the facets of this work, based on more than a decade of research, combine to constitute one of the most in-depth studies of a scientific revolution ever written.