Hilaire Belloc (1870-1953)
From Literary Anecdotes About 20th Century Authors

Three of his books were published in the same season. I [Huddleston] ventured to suggest to him that he was overdoing it. People would not buy three books of the same author at the same time....

'You should, at the beginning, have taken half a dozen pen-names,' I said. 'You have written sixty or seventy books and you have shown a specialist's knowledge of military science, of topography, of finance, and you have written poetry which will endure as long as the language endures. But people like to stick a label on authors. You could easily have made six distinct reputations, whereas skill in many things is considered in our day to be a deadly sin.'
'That may be so,' he admitted. 'I have sometimes thought of it. My advice to a young writer — who is merely thinking of fame — is to concentrate on one subject. Let him, when he is twenty, write about the earthworm. Let him continue for forty years to write of nothing but the earthworm. When he is sixty, pilgrims will make a hollow path with their feet to the door of the world's great authority on the earthworm. They will knock at his door and humbly beg to be allowed to see the Master of the Earthworm.'

From Sisley Huddleston, Paris Salons, Cafes, Studios (Philadelphia, Pa., 1928), pp. 111-112.