In general, use the present tense in writing about a work of literature or an author. Write “Shakespeare includes implicit stage directions in the dialogue” rather than “Shakespeare included.”
Some situations call for the present perfect tense: “Viola tells Malvolio that she has not given Olivia a ring.”
Use the past tense to discuss historical events: “The First Folio was printed in 1623.”
To discuss what is in the First Folio, use present tense – “The First Folio divides the plays into three genres: comedies, histories, and tragedies” – because the book still exists today.