ARCs or Advance Reader Copies of books come out about six months prior to the actual publishing. Because the print runs tend to be small, each individual copy can be $100 or more. Of course they are hard to get your hands on, and even authors often complain that they don't get enough ARCs.
I think in this case, Harry Turtledove (one of my favourite authors) will not complain about this ARC of the final novel in his The War That Came Early series. One of the recipient's greatest regrets was that he might have never known how the series ended.