No, I have not read Friedman's book. In fact, I made my post before your's appeared referring to Friedman. Nor do I need to read his book as the JEDP theory has been around for more than a hundred years. The theory is based entirely on speculation about different styles of writing. Their is no MSS evidence for it that I know of. If there is MSS evidence for it, or if Friedman adds anything new, let me know.
I am well aware that Moses did not actually write Genesis, but compiled and edited it. I also recognize that there were some additions after Moses finished his writing. There is no evidence to suggest that these changed the meaning or that they occurred much later.