There are few authors in which life and work are so closely related as in the case of Joyce: he always wrote about the city where he was born, about the people who lived with him and particularly Nora, his wife, about his readings, and about his peculiar way of understanding the world. And yet, his books are not autobiographical, rather the opposite, as in some way, Joyce is one of the great Realist authors of English literature. Obviously, Realism, either Joyce's or other's, does not respond to predetermined axioms of the critic, but to the sincere and laborious merge between form and the cosmovision of the author. The originality of Joyce and the difficulty of his work come precisely of the unusual fusion of the personal experiences and the abstract, or putting it another way, his life was the path to getting to know Life and Dublin -the Dublin he knew so well- better, the most reliable window to watch exterior reality. If we add that this great creator of words, very close to Shakespeare, did not believe that English was his mother tongue, it is easily understood his genius in the use of the language and the almost unbeatable difficulty of his last book Finnegans Wake. So, starting from the precedents, I will attempt to provide and explain the keys to understand slightly better this literary genius of the 20th century.