When Ernest Hemingway claimed that writers often don't write about the subjects they discuss, it appears that Malcolm Lowry's extensive letter-writing may have distracted him from his fiction writing. Despite this, readers have benefited from Lowry's limitations as a novelist. A notable example is the detailed letter he wrote to English publisher Jonathan Cape on January 2, 1946. In this letter, Lowry passionately rejected a Cape reader's recommendations for cuts and alterations. The letter offers such a thorough analysis of the book's themes and techniques that Granville Hicks described it as "the most careful exposition of the creative imagination" he had ever encountered. Stephen Spender even suggested that the letter be used as the standard preface to Under the Volcano. Lowry characterized his novel as "principally concerned with the guilt of man, with his remorse, with his ceaseless struggling toward the light under the weight of the past, and with his doom."

Under the Volcano, a novel by an author deeply engrossed in his craft, portrays a man consumed by his own demons. It stands as fiction's most powerful representation of the drinker's continuous torment. The Consul's alcoholism serves as a symbol, representing the widespread intoxication of humanity during the period following Franco's triumph in the Spanish Civil War and preceding Hitler's invasion of Poland.

Lowry, in his characteristically humble manner, asserted that his masterpiece "makes provision . . . for almost every kind of reader." He elaborated that it "can be read simply as a story . . . a kind of symphony . . . a kind of opera — or even a horse opera. It is hot music, a poem, a song, a tragedy, a comedy, a farce, and so forth. It is superficial, profound, entertaining, and boring, according to taste. It is a prophecy, a political warning, a cryptogram, a preposterous movie, and a writing on the wall. It can even be regarded as a sort of machine; it works too, believe me, as I have found out."

Even four decades after its debut, critics remain divided over Under the Volcano. In 1984, English critic Ronald Binns observed that "the numerous hiatuses and ambiguities of Lowry's multileveled, mannered, encyclopedic narrative seem positively to invite multiple interpretations."

Biographer Douglas Day lauded the book as "the greatest religious novel of this century" and highlighted five main elements: landscape, characterization, politics, the occult, and religion. Previously, Dale Edmonds, when examining Under the Volcano on an "immediate level," identified five crucial aspects: (1) "The Weight of the Past," referring to the complex connections — both situational and psychological — among the four primary characters; (2) "Salvage Operations," describing the flawed (and unsuccessful) efforts by the other main characters to rescue the Consul; (3) "A Mosaic of Doom," detailing the Consul's involvement with antifascist groups in Mexico that leads to his murder; (4) the Consul's struggle with alcoholism, its potential causes, and its connection to his destiny; and (5) the state of love in the modern era, symbolized by the Spanish inscription on a wall, no se puede vivir sin amar ("one cannot live without loving"), penned by the Spanish Renaissance poet-priest Luis de Leon.

The last component in Edmonds's formulation is crucial. The Consul's tragic flaw is his incapacity to love, which, like in a Greek tragedy, seals his fate to die. He wavers for some time between "either" and "or"—the illusion of Paradise and the stark reality of the abyss. When the decisive moment comes, the Consul never genuinely questions the result. He chooses addiction, destruction, and death.

The two central themes are the crippling influence of the past and its tool — memory — which hinders action and contributes to the Consul's demise. Tragically, he is killed by Mexican fascists, having been misled by his own illusions. Despite being offered an opportunity to rekindle love and its redemptive power, he fails to seize it.