Well, it's OK, except for a lot of things. All the characters speak with the same voice and use the same logic. I'm not sure where the divergence from history happens. Truman agrees with MacArthur (in itself somewhat unlikely) so he goes ahead and goes nuclear. I'd like a little more on how he came to that decision. HT certainly enjoys killing off a lot of people in his books, without much angst.
OK, but if HT believes that Everett, Washington has the same weather as Seattle, he needs to read up on the Puget Sound Convergence Zone.