Priests in Exile is the first comprehensive scholarly opus in English to reconstruct the history of the mysterious Temple of Onias, a Jewish temple built by a Jerusalemite high priest in his Egyptian exile that functioned in parallel with the Temple of Jerusalem.

Piotrkowski's book addresses a topic that is mysterious, important and anomalous: a Jewish community of mercenary priests in the (Egyptian) Diaspora in which the priestly sacrificial ritual was carried out daily over a period of more than two hundred years until the first century CE, outlasting the Jerusalem Temple by about three years.

Although the book focuses on the very circumscribed topic of the parallel Temple it casts a wide net, placing the story in the context of Jewish Diaspora life in ancient times. Ancient topics and texts are brought to bear, including papyri, epigraphy, archaeology, as well as the modern literature. Piotrkowski throws new light on a fascinating episode of ancient Jewish history that is usually left in the dark.