What is the difference in emphasis between the terms science fiction and speculative fiction? Which is The Man in the High Castle?

The Man in the High Castle starts out looking like it fits both categories but then as the story unravels, you realise the novel leans more towards speculative fiction as it revolves around themes like Eastern philosophy, totalitarianism, world histories and also depicts a dystopian world as well as makes references to the I Ching. It was said to be the defining novel of the alternate history sub-genre.The novel delves into power, politics and paranoia as well as incorporates historical events which he then alters in a bold move that gets people thinking 'What if?' Just to note that seeing Hitler had been saved from drowning as a child by a Catholic priest, poses the question "What if?" His novel gives you a glimpse into an imaginary dystopian world where Imperial Japan along with Nazi Germany succeed as the super powers after WWII. Dick was able to empathize with ordinary people who had lived through extraordinary times.He was only one of a handful of writers from the SF category that included actual events from his personal life. His SF novels often mirrored his own life, one that was rooted in an unhappy childhood and poverty throughout his adult life as a writer. According to Brown (p.xi) Dick wrote this novel based on the sub-genre of SF that was less well known at that particular period of time. Brown (2001) states that the 'perception of reality' was a consistent theme in Dick's novels. Another theme that held a fascination for him was war, despite that he both feared and loathed it.The novel is about ordinary individuals whose lives are interconnected through their actions.He includes a mix of totalitarianism and Eastern philosophy. Brown (2001) believes "The Man in the High Castle" was Dick's finest work and won a Hugo award. 

        

Reference:

Brown, E. (2001). Introduction. In Dick, P.K., The Man in the High Castle (p.v-xii). London: Penguin 
Dick, P.K. (2001; 1962). The Man in the High Castle. London: Penguin.
http://www.goodreads.com/author/show/4764.Philip_K_Dick
http://en.wikipedia.org/wiki/Philip_K._Dick