Voyage to Arcturus
I am a great fan of VOYAGE TO ARCTURUS by David Lindsay (published in 1920), and consider it one of the best books of the fantastic ever.
Let me try to justify that astounding statement. The book was one a deep theme, rich with invention, and daring in its mystery.
( more here )The sense of wonder for which science fiction authors try is limited by their materialistic outlook. For a sense of the truly fantastic, oriental wonders as dazzling and strange as life itself, one needs to move into something like the spiritual hallucination and symphony of Dunsany.
I will not call it a good science fiction book, and I am not sure if it would be classed, these days, as fantasy. It is a work that stands alone.