|Right: Goethe's 1809 Elective Affinities, the source of inspiration for the majority of most literary realism authors, such as: George Eliot, Honore Balzac, and Benito Galdos, to name a few. Left: George Eliot's 1872 Middlemarch, philosophically based in part on Goethe's Elective Affinities, an example of "literary realism".|
On 23 Oct 1799, German polyintellect initiated the subject of “literary realism”, when he complained to his friend Friedrich Schiller about the lack of realism in the work of French author Prosper Crebillon (1674-1762); specifically, according to Goethe:
“Crebillon … treats the passions like playing cards, that one can shuffle, play, reshuffle, and play again, without their changing at all. There is no trace of the delicate, chemical affinity, through which they attract and repel each other, reunite, neutralize [each other], separate again and recover.”
Goethe, in short, stated to the effect that Crebillion's writing is not realistic in the sense that it is not based on the way that people "react" to each other, according to the principles and outcomes of chemistry.
In 1809, Goethe published his physical chemistry based realism novella Elective Affinities, wherein each character is considered to be a chemical, and each chapter is considered to be a different chemical reaction and or mechanism of the grand reaction tale of the novel.
In 1889, German natural science popularizer Wilhelm Bolsche, in his essay “Goethe’s Elective Affinities in Light of Modern Science”, argued that the Goethe's Elective Affinities novel is realistic, and a and is a pioneering work of literary realism, due to its portrayal of natural forces and psychology, and that it should be seen as a predecessor to such realistic works such as George Eliot, who mentally absorbed the logic of Goethe’s human chemical theory, and Honore Balzac, who likewise mixed affinity theory, chemistry, and passions together in his works. 
In 1959, Gunter Grass published his The Tin Drum, wherein the lead caries around a few pages of Goethe's Elective Affinities mixed with some pages from Rasputin, as a guidemap to the world, which is a novel part allegory, myth and legend, placing it in the genre, supposedly, of magic realism.
In 2010, Charlotte Bolsche, in her chapter section “Realism in Literature and the Laboratory”, stated that the two leading realism authors are: Goethe (Elective Affinities, 1809) and his vicarious student George Eliot (Middlemarch, 1872). Emile Zola also is counted among realism authors. 
Others list French writer Stendhal and Russian writer Alexander Pushkin as among literary realist authors.
Spanish realism novelist Benito Galdos’ 1887 Fortunata Y Jacinta, said to be based on Goethe's Elective Affinities relationship determinism philosophy, together with Spanish novelist Leopoldo Alas’ 1885 La Regenta (The Judge's Wife) are said to be the most popular and representative novels of Spanish literary realism. 
The major realist writers, according to Josh Rahn (2011), are the following: 
● Honore Balzac
● Fyodor Dostoyevsky
● George Eliot
● Gustave Flaubert
● Henry James
● Mark Twain
● Dean Howells
● Edith Wharton
The following are related quotes:
“The dominant paradigm in novel writing during the second half of the nineteenth century was no longer the romantic idealism of the earlier part of the century. What took hold among the great novelists in Europe and America was a new approach to character and subject matter, a school of thought which later came to be known as realism. On one level, realism is precisely what it sounds like. It is attention to detail, and an effort to replicate the true nature of reality in a way that novelists had never attempted. There is the belief that the novel’s function is simply to report what happens, without comment or judgment. Seemingly inconsequential elements gain the attention of the novel functioning in the realist mode. From Henry James, for example, one gets a sense of being there in the moment, as a dense fabric of minute details and observations is constructed. This change in style meant that some of the traditional expectations about the novel’s form had to be pushed aside. In contrast to what came before, the realistic novel rests upon the strengths of its characters rather than plot or turn of phrase. The characters that the realistic school of novelists produced are some of the most famous in literary history, from James’ Daisy Miller to Dostoyevsky’s Raskolnikov. They are psychologically complicated, multifaceted, and with conflicting impulses and motivations that very nearly replicate the daily tribulations of being human.”— Josh Rahn (2011), “Realism”, The Literature Network 
1. (a) Bolsche, Wilhelm. (1889). “Goethe’s Elective Affinities in Light of Modern Science” (“Goethes Wahlverwandtschaften im Lichte moderner Naturwissenschaft”), Publisher.
(b) Tantillo, Astrida O. (2001). Goethe's Elective Affinities and the Critics (pg. 80). Camden House.
2. Sleight, Charlotte. (2010). Literature and Science (§4: Realism in Literature and the Laboratory). Palgrave Macmillan.
3. Fortunata y Jacinta – Wikipedia.
4. Rahn, Josh. (2011). “Realism” (Ѻ), The Literature Network.
● Literary realism – Wikipedia.