Threshold Phenomena reexamines Jacques Derrida's thinking of hospitality, from his well-known writings of the 1990s to his recently-published seminars on the same topic. The book follows Derrida's rereading of several central figures and texts on hospitality (Sophocles' Oedipus at Colonus, Kant's Perpetual Peace, Levinas's Totality and Infinity) and his attempt to rethink questions surrounding not only private but also public hospitality in the form of immigration law, the contemporary treatment of migrants or stateless peoples, and the establishment of cities of asylum.

Naas develops many of the central themes of Derrida's seminar-the relationship between hospitality and teletechnology (telephone, internet, cyberspace, etc.), the role of fatherlands and mother tongues in hospitality, questions of purity, immunity, and xenophobia, and the possibility of extending hospitality beyond the human-to animals, plants, gods, and clones. Reframing Derrida's approach to ethics, Naas reconsiders the relationship between hospitality and deconstruction, concluding that hospitality is not merely a theme to be treated by deconstruction but one of the best ways of describing its work.

Naas's book turns around a figure that Derrida himself returns to several times throughout the seminar: the threshold-a figure of hospitality par excellence, but also, in his seminars, another name for what Derrida in the 1960s began calling differance. Threshold Phenomena concludes that Derrida's seminar on hospitality is one of the best introductions we have to Derrida's work in general and one of the surest signs of its continuing relevance, a seminar that is at once fascinating and engaging in its own right and necessary for analyzing today's increasingly nationalistic and xenophobic political climate.