I disagree with Alexis de Tocqueville's remark, Literature may work through grammar syntax and semantics but there are no actual standards that would make a piece of work qualify as literature.
Authors such as; Mark Twain, who had a distinctive style of writing, helped give a strong description to his works and a vivid sense of realism. Mark Twain was known for writing in a carefree style. In the first bit of 'The Adventures of Huckleberry Finn,' the style of writing was unrefined and raw and it was slightly difficult to understand since it was filled with slang. However, it became clear that the character in his work was meant to give off a carefree aura. Aside from the dialect that Mark Twain used he also used an imagery sense of realism to his settings and characters, this allowed the reader to understand the characters a bit more. In Mark Twain's writings, he was able to interact with deeper meanings and underlying themes through simple stories.
Another example that could be taken is of; Edgar Allan Poe, his use of terror made him famous as a popular gothic writer. His writings were a way to express political sentiments, particularly regarding racism, slavery and social distinctions. He was known for his eerie writing style, which was created through his use of punctuation. The tone of his work would be set by his word choice and his descriptive writing. Poe believed that his punctuation made a point, this allowed the reader to feel the full effect of the sentence. Poe's writings were usually based on revenge, murder, and other sorts of eerie themes, this would leave the reader to determine the cause of motives.
Poe also used other different tools that would captivate his audience.
Mark Twain and Edgar Allan Poe were both amazing writers in the 19th century, they both had a unique sense of writing and were not mainstream writers. Even though their work was different from other, but that does not mean that their writings were not a proper form of literature.
