“Zarathustra” is my brother’s most personal work; it is the history of his most individual experiences, of his friendships, ideals, raptures, bitterest disappointments and sorrows. Above it all, however, there soars, transfiguring it, the image of his greatest hopes and remotest aims.

Thus Spake Zarathustra by Friedrich Nietzsche
INTRODUCTION BY MRS FORSTER–NIETZSCHE