A note of caution about the mathematics: Here's what Friedman writes in his preface:

Michael Friedman wrote:The present book makes heavier mathematical demands than the reader may be used to in the philosophy of science. Unfortunately, given the way in which physical and philosophical problems are intertwined with mathematical notions here, especially with the notion of general covariance, there is no practicable alternative. In particular, one has to see in detail how one goes from generally covariant formulations to the more usual formulations and back again if one is to attain any real clarity about the various relativity principles. Of course, these formulations and methods are in no way original with me. I have taken them, with minor alterations, from the works of Anderson, Trautman, and Havas, mentioned above.* In any case, I have striven to make the treatment as intuitive as possible via numerous pictures and diagrams, and I have included an appendix outlining the geometrical techniques employed. All that is absolutely presupposed is an acquaintance with the basic ideas of analysis and linear algebra on the level of an undergraduate course in advanced calculus.

*He is referring to writings in the '60s by J.L Anderson, A Trautman, and P. Havas. Friedman has an extensive bibliography from which he draws,, which if interested, I can retrieve for anything Friedman refers to. Anderson, for example, will play an important part. Indeed, in an earlier part of the preface Friedman provides his growth from his dissertation to this book on this very topic. My first acquaintance with Friedman was when I was doing my thesis work on Kant's space and time. His book: "Kant and the Exact Sciences" was both thorough and enlightening. I also have his book: "Revisiting Logical Positivism."

One of the advantages of this book is that, for those that are unacquainted with the roots of relativity theory, both scientifically and philosophically, this book will fill that void. Not in detail, but with clear direction. And this is where I will start. That story, of course, is oft-told, and anyone who is really interested in it will discover the volume of interest in it. Indeed, as any scholar will tell you, once you launch your project, you will be confronted by what appears to be an endless effort wading through it all. Your first trial will be one of "data-reduction.", which in my case turned out to be a challenge too great to fulfill. (Well, there were other factors as well.)

In any case, I hope you will find in it something you might not have realized. And more than that, I hope myself to get clear about the concepts being used. Perhaps you will find your own position a bit shakier than you might otherwise have thought, as well.

James