As far as I know, prior to the release of this guidebook, the Kings Canyon High Basin Route had never been identified or hiked as a continuous route.
But I am absolutely certain that it has all been done before. Personally, by the end of the 2014 season I had hiked all but 13 of its miles, plus most of its alternates. I most definitely am not the only one to have traveled these routes, or the first.
The High Sierra has been thoroughly explored. While there may still be a few areas where no man has been before, it’s very unlikely that there is a practical reason reason to go there, e.g. to hunt game, trade goods, mine precious metals, and graze livestock — and, in more recent times, to climb a peak, catch hungry fish, or simply travel through.
In-depth descriptions of the trails, valleys, and passes that make up the KCHBR, plus adjacent peaks and much more, can be found in The High Sierra by R. J. Secor, at the website High Sierra Topix, and in myriad online trip reports.