In 1926, Arthur Conan Doyle did something unusual. After decades of Sherlock Holmes stories narrated by Dr. Watson, he let Holmes tell his own case. The Adventure of the Blanched Soldier. Holmes himself, unfiltered, wrote the whole thing.
It was awful. Not factually wrong, though; Holmes catalogued every detail with surgical precision (like the cigar ash and the chemical residue on the suspect’s left cuff), but it was completely unreadable.