Mary Godolphin - Robinson Crusoe in Words of One Syllable (1867)
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Though intended as a children's book I prefer to think of this as a proto-Oulipo text though admittedly the distortion is fairly trivial all things considered. I also can't help but wonder if in fact it's any easier for a child to read one-syllable words.
Mary Godolphin hit on this idea and ran with it. She produced similar syllabically restricted versions of Pilgrim's Progress, Swiss Family Robinson, Aesop's Fables and a now-forgotten book called The History of Sanford and Merton. Godolphin was the pseudonym of Lucy Aikin (1781-1864), a popular historian (Memoirs of the Court of Queen Elizabeth is best-known), biographer of Addison, translator and children's writer. She was a respected letter writer and at least two collections were later published. Robinson Crusoe was the first of her one-syllable books and the rest from then until 1870.
Sharp-eyed readers are probably exclaiming, "Now hold on, Mr Blogger Person! How can she have written seven books years after her death? You are surely a shoddy researcher, sir!" Well, that stings a bit and nevertheless I have no good answer. The Cambridge Bibliography of English Literature: 1800-1900 has the same dates so it's not as if I'm pulling dubious dates off the Internet. Well I did but I double-checked them. The Encyclopedia of Romantic Literature (edited by Frederick Burwick) also notes this discrepancy, only saying that the book were published posthumously but giving no explanation otherwise. Why she would have written but not published these is a mystery, as is why her heirs would wait three years and then not use a marketable name but keep the identity secret.
I actually wonder if this attribution of the pseudonym is mistaken. I can't find a contemporary reference to it which is odd for such a well-known writer and none of the "One Syllable" books indicate anything as far as I can see. In fact the Swiss Family Robinson book says the author was "encouraged" by the reception of the earlier book "to add to her works" though the indication she was alive doesn't mean she in fact was. The 1874 Bibliotheca cornubiensis says Godolphin is a pseudonym but provides no other identity. Trade listings and ads from the late 19th century (and a review from The Spectator in December 8, 1883) don't indicate anything other than the Godolphin name. Though it has no direct bearing it's worth noting that editions published by Henry Altemus Company in Philadelphia omit the Godolphin name - perhaps they were pirated?