[…] Tolkien’s most important contribution by far […] was his construction of a systematic secondary world. There had been plenty of invented worlds in fantasy before, but they were vague and ad hoc, defined moment to moment by the needs of the story. Tolkien reversed that. He started with the world, plotted it obsessively, delineating its history, geography and mythology before writing the stories. He introduced an extraordinary element of rigour to the genre.
China Miéville – Tolkien – Middle Earth Meets Middle England