The World as Will and Representation is the main work by Arthur Schopenhauer, a German philosopher (1788-1860). He had an immense influence on the European philosophical traditions, especially within metaphysics, aesthetics, ethics, morality, psychology. Arthur Schopenhauer himself was inspired by the transcendental idealism of Immanuel Kant, from which he build his own atheistic metaphysical, read the Wikipedia article about him for more.
Fun fact: Schopenhauer read the old Hindu texts, the Upanishads, and he was so impressed by the Vedic philosophy that he called them “the production of the highest human wisdom”, and he believed the ancient works to contain superhuman concepts.
This version og The World as Will and Representation is the two-volume translation from German to English by E. F. J Payne. The volumes are merged into one PDF-file.
Download The World as Will and Representation by Arthur Schopenhauer here as a free PDF e-book (558 pages/23 MB):