The Secret History of the English Language by M. J. Harper is a short, entertaining book. That is about all it is. The author applies his understanding of epistemology to the subject of the English national creation myth. His idea is that everything we know is wrong. Not just about the people and language of Britain but of the whole of human existence. He begins by making what appear to be several good points; that what we know about the history of Britain often makes little sense if we think about it, that Latin may be descended from Italian rather than the other way around, and that English may be closer to the root language of western Europe than the Romance languages and the Germanic languages. After much snark at the expense of the academics, who he seems to think little of, he gets on to other subjects that could be used in examining pre-history, geology and Darwinian evolutionary theory. At this point in the book, he brings into question his own ideas by showing he is woefully misinformed about both of the other subjects in his book.
I only know enough about geology to know that he is not entirely accurate in his description about how the science works. If what he said were actually true, geology wouldn't be a science at all. He seems to think they don't use the scientific method; they just get an idea, teach it to the next generation, and go on believing it and spreading it with no justification, even after it is proven wrong. This is dogma, not science, and it is not how geology works.
Then comes biology. He seems to think that all of evolutionary theory is based on fossils. That couldn't be farther from the truth. Even Darwin recognized 150 years ago that fossils, while being nice to look at and helpful in confirming some theories, are not necessary at all to demonstrate that evolution happens. Since Darwin's time, the science has expanded to include the studies of genetics and protein changes throughout lineages (The name for this subject escapes me at the moment). Simply because no existing species are the ancestor species of modern species, which is not entirely true, he thinks the entire theory is false, or at least should be reexamined. While this is a slightly better argument than I've heard from any creationists, it is still based on willful ignorance. I say willful because the process of writing a non-fiction book is supposed to involve research to ensure your examples are correct.
While the linguistic hypotheses in this book are interesting, they are diminished by the lack of accuracy in the geology and biology sections. I can't even see a reason for those sections to be in the book except to say that anything anyone knows in those fields must be wrong because they are widely agreed upon subjects. All Applied Epistemology is about is ripping to shreds anything that people know because they know it. This is an admirable thing to do when there are actual problems with the theory, but it is out of place in the non-linguistic portions of the book. Because of the author's lack of understanding of biology and geology, I wonder if maybe he misunderstands linguistics and history as well. His ignorance in other fields calls into question his entire supposition. The book may have had more impact and been more believable if he had avoided the mention of the other subjects. It certainly would have been more cohesive.
I was entertained by this book. Until I reached the physical sciences portions, I felt informed by it. Now, I question everything I read. Could the author have done as little research on the subject of western languages as he did on the subject of biology? It is hard to imagine that he did, but by writing page after page of uninformed drivel, he certainly invites the reader to question the entire book. He is most certainly hoping that the reader is as uninformed on those subjects as he is. As the target audience of this book seems to be students of English and English history, the majority of readers are likely to be ill-informed on those subjects. As a result, this book is likely to introduce concepts that have little basis in reality alongside common misconceptions about other sciences, doing nothing for the advancement of any knowledge whatsoever.