Art and Theory of Art: Foundations of a New Aesthetics CW 271 by Rudolf Steiner. Containing an Author's Summary 1888; Four essays written between 1890 and 1898; eight lectures held between 1909 and 1921. Translated by Dorit Winter and Clifford Venho.
The whole book as a zip file.
I. WRITINGS & ESSAYS
1. Goethe as Father of a New Aesthetics (1888)
2. On the Comical and Its Relationship to Art and Life (1890-1891)
3. Beauty and Art (and the next short piece) Count Leo Tolstoy: What Is Art? (1898)
4. On Truth and the Illusion of Truth in Works of Art (1898)
5-1. The Being of the Arts (Berlin, October 28, 1909)
6-2. The SensorySuprasensory in Its Realization through Art, I (Munich, February 15, 1918)
7-3. The SensorySuprasensory in Its Realization through Art, II (Munich, February 17, 1918)
8-4. The Sources of Artistic Imagination and Suprasensory Knowledge, I (Munich, May 5, 1918)
9-5. The Sources of Artistic Imagination and Suprasensory Knowledge, II (Munich, May 6, 1918)
10-6. SensorySuprasensory: Spiritual Knowledge and Artistic Creativity (Vienna, June 1, 1918)
11-7. The Suprasensory Origin of Art (Dornach, September 12, 1920)
12-8. The Psychology of the Arts (Dornach, April 9, 1921)