Hitler's rise to power is usually explained by honing in on the major events, the Treaty of Versailles, German anti-semitism and the Great Depression. While these were indeed important triggers, starting a political party from scratch, particularly in such a time during the Weimar Republic, was an extremely ambitious endeavor, particularly when you don't have money.
During the early days of the Nazi party, there were several instances when it could've gone belly up, in 1923 during the failed Putsch, in the late 20s as the economy was picking up, and even during the 1930s as they vied against a growing communist revolution. Pool does a good job of identifying which businesspeople and who among the aristocracy reached into their pockets to stave off communists by seeing Hitler as a lightning rod that could move the general masses, as every other politician was seen as incompetent for the working class.
Nazism, even from a purely economic standpoint, was never a sustainable ideology. It needed backers in order to sustain itself, both before and after it took power. It's primary raison d'etre was to crush communism, and so funding the Nazis was not even purely a local affair, as Pool mentions all the international backers of Hitler, such as British royalty, Henry Ford and many others around the world who merely wanted to see the collapse of communism not only in Germany, but where it was gaining power, the Soviet Union.
Much of this is lost in the narrative of WW2, and reading this book gives a more clear picture of what motivated it to begin with.