This volume provides annotated translations of the primary sources, which were largely in German, leading up to Einstein's theory of general relativity, in which Einstein attempted to extend his theory of special relativity beyond space and time, to include matter and gravitational fields, by introducing gravity through his "equivalence principle" - the equivalence of gravity and acceleration. This resulted in Einstein rejecting the second postulate of his theory of special relativity - the postulate on the constancy of the speed of light - in the presence of a gravitational field. This review reveals that Einstein's theory of general relativity it is not a theory of gravity; it is a relativistic theory about the effects of gravitation, or more strictly, of a uniformly accelerated reference frame. There is nothing in any version of this theory that represents or explains or provides any connection to the weak attractive gravitational force between matter. In order to make calculations with his theory, Einstein had to import Newton's empirical law of gravitation. Consequently, the only evidence that Einstein could provide for his theory of general relativity was effectively Newtonian. Part I reviews Newton's laws of motion and of gravitation, his definitions of inertial and gravitational mass, and his equivalence principle, which provide the background to Einstein's theory. Part II provides a detailed analysis of the development of Einstein's theory of general relativity. Part III provides a postscript on subsequent developments, and the Conclusion. In the light of the continued failure of Einstein's efforts to overcome the main objections to his theory of special relativity - the Ehrenfest paradox, and its failure to explain the observed Doppler redshift and blueshift of light - or to provide any evidence for it, and in the absence of any supportive evidence for his theory of general relativity, both theories must be rejected until such objections are overcome and such evidence is provided.