A modern man is thrust into a supernatural conflict when he discovers an ancient, cursed artifact that transports him to a vessel sailing upon a mystical sea. John Kenton finds himself aboard the Ship of Ishtar, a floating sanctuary caught in a perpetual war between the goddess Ishtar and the god Nergal. He must navigate the treacherous politics of the ship's crew and the supernatural forces vying for control of the vessel. The narrative utilizes a portal-fantasy framework to contrast the mundane reality of the protagonist with the high-stakes, mythic environment of the ship. Kenton faces physical threats from monstrous entities and logical constraints imposed by the divine rules governing the ship's existence.

Readers frequently highlight the ornate and descriptive prose style that defines Merritt's approach to world-building. Discussion often centers on the contrast between the fast-paced action typical of pulp magazines and the author's tendency toward dense, sensory-rich passages. Critics note that the work serves as a prime example of early fantasy conventions, particularly in its use of lost civilizations and mythological conflict. The balance of character development is often secondary to the atmospheric immersion and the imaginative scope of the setting. Readers who appreciate classic, stylized fantasy often find the work a significant artifact of the genre's formative period.