Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Greatest book of the 20th century

Quite simply the most important book of the twentieth century for several reasons:1] Spengler offers a morphology of history as an organic conception that can used to understand all historical development with genuine insight.2] Spengler's projection of coming trends (e.g. Militant Islam, environmental crisis, secularization of the elites, "second religiousness" of the folk, etc.) has enormous predictive value. His understanding of current events (from the perspective of 1917!) is more acute and useful than any present day commentator.3] Without a doubt, Spengler is the most important National Bolshevik thinker.4] "Oswald Spengler is the greatest mystic of the twentieth century." - Klemmens von Klemperer