Nietzsche regarded Thus Spoke Zarathustra to be one of his most important works. Ultimately, it is a work about overcoming the self. It combines inverted allusions to the Bible with Greek mythology and ancient Persian religion.
Nietzsche composed the work over a period of two years, the first part being written in only ten days. Nietzsche himself considered Thus Spoke Zarathustra to be one of his most important works, and it is considered by many commentators to be the most detailed explanation of his ideas on the "overman" and "the will to power." He originally only wrote three parts to the book, feeling that the ending was best completed as Zarathustra discovered the doctrine of the "eternal recurrence" on his mountain. He later wrote a fourth part that he refused to publish, claiming that it was too blasphemous for public consumption. The fourth part circulated amongst his friends in a manuscript draft until it was finally published by his sister after Nietzsche had succumbed to his insanity.
Thus Spoke Zarathustra is also one of Nietzsche's most popular public works. Although it received only mild acclaim when it was first published, it gained in popularity after Nietzsche's death and has continued to be his best-selling work in modern times. During the Second World War, the German government had over 100,000 copies of the book printed and distributed to the army along with copies of the Bible.
On a narrative level, the book is about the travels and teachings of Zarathustra, a mythical, religious, prophetic teacher who has come to bring the teaching of "the overman" to the world. Zarathustra's teachings are a combination of ancient religious texts such as stories from the New Testament and Greek myths. The narration of the book is sparse. Instead, the work centers on Zarathustra's teachings of the overman and his internal struggles to overcome aspects of the world that will ultimately bring him to the doctrine of the "eternal recurrence," a state associated with ultimate transcendence.
The book recounts Nietzsche's view of "the overman," a state of pure being in which one can love nature and the earth as the highest good. The book famously elaborates on Nietzsche's belief that "God is dead," a teaching Nietzsche originally developed in his book The Gay Science. In Thus Spoke Zarathustra, Nietzsche envisions a world in which the overman can overcome the teachings of a dead Christianity to come to a greater eternal return.
The experimental style of the book kept it from becoming popular in academic and philosophical circles until after Nietzsche's death. The book's often-ambiguous style did not fit well with the philosophical style of late 19th and early 20th century writings. However, the late 20th century postmodern philosophical community embraced the work and its boundary-breaking format, which blended philosophy with a critique of religion and society. Many postmodern theories of deconstruction have been based on Nietzsche's work in Thus Spoke Zarathustra, and the book continues to produce new academic works of interpretation. Today there are hundreds of commentaries and expositions on what has proved to be Nietzsche's most famous work, and it continues to influence new generations of philosophy.