This book cannot be taken seriously. Matlock claims that all religions, and especially Judaism, derive from early 'objectivist' Hinduism ('Yishvara'), which he regards as a nature religion involving reincarnation and seven basic rules of conduct. To this end he revises the history of Hinduism and other religions and makes highly dubious claims about the mindsets of modern believers. He regards most current forms of Hinduism as 'Aryanist' and 'subjectivist' distortions. In some passages he actually proclaims that all people - even professed atheists - are automatically 'members' of Yishvara.
Matlock supports his basic claims by uncritically citing a mixture of ancient pseudo-historical and religious texts (read literally or metaphorically, as it suits him) and recent fringe Indian or pro-Hindu thinkers. In many cases he simply makes unsupported assertions.
A prominent feature of the book involves 18th-Century-style philology, often relying on very loose similarities indeed. Matlock tries to argue that many words in a range of languages come from Sanskrit or Kashmiri (he thinks that Kashmir had important early contact with Judaism), that everyone once spoke Sanskrit, that the Munda languages of India are an important source for German, etc, etc. But most of his alleged cognates - invented by him or taken from unreliable Indian sources - are ludicrously wrong or (where less is known about the etymology) very implausible.
On non-linguistic fronts, Matlock develops a complex quasi-occult philosophy based on Hindu notions extended to cover St Patrick's Ireland, Old Testament Israel and the contemporary USA. He also gives an idiosyncratic account of the relation between faith (good) and belief (bad) - although he admits that he himself does not follow this in his book. He identifies his own approach as 'scientific' and 'empirical', and redefines the notions of science and rationality so as to exclude skepticism which rejects the paranormal. His own canon of empiricism involves nothing stronger than the agreement of more than 'a few' witnesses, and often only his own subjective or unverified experiences and impressions. Matlock makes various attempts to appear intellectually respectable, eg by criticising 'Outer Space cultists', but his own use of evidence/argumentation is no better than that of von Daniken and such, and he even accepts Atlantis as real.
I cannot recommend that readers buy this book. It will only annoy the well-informed and confuse newcomers to the field.