Joseph did not publish any other works before the Book of Mormon but he also did not write much at all before 1832. Studying Joseph’s other writings only emphasizes that he was not educated enough to compose the Book of Mormon.
Robert A. Rees said:
What do we have from Joseph’s pen before the publication of the Book of Mormon in 1830? According to Dean C. Jesse’s The Personal Writings of Joseph Smith, very little: a note summarizing Martin Harris’s experience with Charles Anthon, possibly written in 1828, and a letter to Oliver Cowdery dated 22 October 1829. His handwritten account of the First Vision written in 1832 is ungrammatical, is written with little sense of punctuation or compositional structure, and, though sincere and authentic, shows little evidence of stylistic or compositional competence or confidence. Certainly there is evidence of the beginnings of an eloquent voice, but that voice is tentative and immature.– Robert A. Rees – Joseph Smith, the Book of Mormon, and the American Renaissance: An Update
How would Joseph have been able to compose the Book of Mormon three years earlier based on what we see in his first vision account? Isn’t the evidence from his own writing consistent with descriptions of his general lack of education?