There is no equally-named Kemp on arxiv.org (there is a "R.Kemp", where "R." seems to stand for "Roger" in two solid-state chemistry/physics papers), and there are no google hits with his name and +site:.edu.
On http://www.superprincipia.com/About_The_Author.htm is the author's CV, he is essentially a radar engineer (probably a good one given the companies he worked at), and worked as a math teacher at some time. In the autumn of 1989 he suffered an attack of Holy Spirit and seems not to have recovered yet.
Unfortunately the website gives no sample chapters for download. I'd expect the book to be a stylistically pleasant reading, but I cannot tell if the hard core physics stuff is correct (and free from esoteric stuff). When in doubt, I'd stick with Penrose (his two-volume book with Rindler is great, his popular stuff as well (except when he tries to push his unorthodox interpretation of quantum mechanics)).
The wensite says the book requires "basic understanding into algebra, geometry, differential calculus, and integral calculus". Since that little math is not even sufficient to understand the currently generally accepted theories of physics (one needs at least differential geometry, algebraic topology, functional analysis and Lie groups for even the simplest things), I have some doubts whether the book really *explains* physics or just tells a story *about* physics.
The fact that he has no PhD should not matter (he seems not to want one), and even Einstein got PhD his only a year after Special Relativity.
His paper about photons is mostly prose with very few equations in between, and sounds strange (to say it mildly), which has already been mentioned by other commenters here.
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