Although "Island of the Three Marias" refers to a real geographic place, the poem draws on the literary tradition of islands as locales of the exotic and the fantastic. Umberto Eco's Island of the Day Before and H. G. Wells' Island of Dr. Moreau are two well-known examples in this tradition. Ríos' poem appears in the second section of his 1985 collection, Five Indiscretions. The collection as a whole addresses themes of gender, sexuality, and desire, and the section in which "Island of the Three Marias" appears deals with representations of masculinity and martyrdom. The poem, consisting of six free verse stanzas—alternating quatrains and longer stanzas—presents brief descriptions about three men who live on one of Las Islas Marias (The Mary Islands), a group of four islands that are ninety miles off the southwestern coast of Mazatlán,Mexico. Although readers are not explicitly told, the men are either convicts or employees of Islas Marias Federal Prison, which was established on the largest island, Maria Madre, in 1905.

Ríos hones in on a detail of each of the men's lives, letting that detail serve as a symbol for the life as a whole. Even though the poem refers to a real place, like many of Ríos' poems, it has a fantastic and fabulous feel about it and an elegiac tone. Other poems in the section, such as "A Man Walks as if Trapped," "A Man Then Suddenly Stops Moving," "The Carlos Who Died and Left Only This," and "On January 5, 1984, El Santo the Wrestler Died, Possibly," have a similar tone, and all make attempts to symbolically sum up the essence of a particular man's life. Ríos' style is often described as magical realism, a term made popular by Latin American authors such as Gabriel García Márquez and Jorge Luis Borges. Magical realism combines the dreamlike elements of myth and fairy tale with the sharply etched description of everyday events.