The plot of the movie mostly focuses on the second part of Lost Illusions, the novel it adapts, called "A Great Man of the Provinces in Paris".
The character of Nathan d'Anastazio, played by Xavier Dolan, is actually a synthesis of three characters from the novel: Raoul Nathan, a scheming journalist, Daniel d'Arthez, a hard-working writer and Melchior de Canalis, a successful poet.