"The Waning of the Middle Ages" is a historical analysis of the cultural life of the late Middle Ages, particularly in France and the Low Countries, during the 14th and 15th centuries. It delves into the period's modes of thought, forms of expression, religious beliefs, and social norms. The book argues that the era was characterized by a highly stylized and overwrought civilization, marked by an excessive emphasis on chivalry and courtly love, a religious mindset dominated by the fear of death and the afterlife, and a cultural milieu that was both highly imaginative and deeply pessimistic.

"Tractatus Theologico-Politicus" is a seminal work that explores the relationship between religion, politics, and philosophy. The author argues for the separation of theology and philosophy, asserting that the purpose of the state is to promote peace and security through rational governance, free from religious influence. He critiques the role of organized religion in politics and defends the freedom of thought and expression, advocating for a secular, democratic political order. The work also delves into biblical criticism, challenging traditional interpretations and suggesting that the Bible should be analyzed through a historical and contextual lens.

"Coplas por la muerte de su padre" is a collection of elegiac verses written in memory of the author's father. The poems explore themes of mortality, the fleeting nature of life, and the inevitability of death. The author uses his personal grief as a platform to delve into philosophical reflections, ultimately presenting a stoic acceptance of death as a natural part of life. The work is widely regarded as one of the greatest achievements in Spanish poetry.

"Castaways" is a historical narrative that recounts the experiences of an early Spanish explorer who, along with his crew, shipwrecks off the coast of Florida. Stranded in unknown territory, the survivors must learn to adapt to the harsh environment, interacting with native tribes and navigating through unfamiliar landscapes. The story is a testament to human resilience and the profound impact of cross-cultural encounters during the age of exploration.