Is The Man in the High Castle science fiction?

Alternate history is one of those subgenres that's typically associated with science fiction, but there's nothing inherently "science fiction-y" about it.  Certainly, you can't claim that it's a part of "normal" non-speculative fiction since its version of history is alternate.   In addition, many of its most famous examples, including such classics as Harry Turtledove's The Guns of the South, use science fiction-y elements like time travel to create the alternate realities in which they occur.  On the other hand, there are plenty of examples of works in which the only speculative device the author uses is the alternate history itself; one of the most notable of these is the work that I'll be focusing on today: Philip K. Dick's Hugo-winning novel The Man in the High Castle.