Gilbert Keith Chesterton (1874-1936) was born at 32 Sheffield Terrace, Campden Hill, London. He was an absent-minded child, and a slow developer: he did not learn to read until he was eight. He soon became a passionate reader, especially of fairy-tales, and was a lover of toy theatres. After St Paul’s School he took classes at University College London and at the Slade School of Art. He decided to become a writer rather than an artist. He made his name as a reviewer and essayist in the 1890s, and published his first books in 1900, in the same year that he met the man who became his close friend, Hilaire Belloc.
In 1904 he published his first novel, The Napoleon of Notting Hill, set in an indeterminate future in which London had become Balkanised. His most famous novel came in 1908: The Man Who Was Thursday: A Nightmare, a surreal fantasy set again in London. Other less significant works of fantasy, both in books and plays, are discussed in the Science Fiction Encyclopedia.
By 1914, Chesterton had written the best of his fiction, and his later career is marked rather by his religious writing. See here for his life during the Great War. The death of his brother Cecil Chesterton in France in the last weeks of the war in 1918 had a serious effect on him, as did his friendship with the Catholic writer Belloc, and in 1922 he was received into the Catholic Church. His religious writings include St Francis of Assisi (1922); The Everlasting Man (1925) and St Thomas Aquinas (1933). The great Aquinas scholar Etienne Gilson said this last book showed a deeper insight into Aquinas than professional philosophers had achieved.
This information is largely taken from Bernard Bergonzi’s article in the Oxford Dictionary of National Biography 11 (2004).