Modern physics is based on two paradigms that emerged from the Second Scientific Revolution - relativity and the quantum. Since their inception these two theoretical giants have advanced science and society far beyond anything that their originators could have even dreamed up, but in a sense they seem to be progressing in different directions and are regarded mutually incompatible. Yet they come to a point in history where the next step in their own advancement would be to unify into a single overwhelming physical paradigm. The concept of unification is well known in relativity theory with many attempts dating from just a few short years after Einstein first developed relativity. But the hyperspace unification that seems to have originated with Kaluza in 1921 and was modified by Klein a few years later has become the best known attempt. This book has two parts. The first, Hyperspace, deals with the original Kaluza theory in all of its aspects and incarnations up until the 1960s. After the 1960s the idea of unification was adopted by quantum theoreticians based on their belief that the quantum is more fundamental than relative space-time. However, since the 1980s Klein’s adaptation of Kaluza’s theory has been used to unify physics under the quantum banner as has the purely quantum theory Standard Model. Yet both of these quantum attempts have fundamental problems that can only be solved by returning to Kaluza’s original theory as modified by Einstein and Bergmann in the 1930s. So the second part of the book, Continuum, tells the rest of the story and offers a new theory, a five-dimensional single field theory, the merges the best of both paradigms together. By merging the two paradigms instead of replacing one by the other, single field theory preserves all of the many successes of both theories. This is the book that every physicist, physical scientist and non-professional science advocate should read and every theoretical physicist and physics students must read.