"The Dawn and Twilight of Zoroastrianism" R. C. Zaehner, 1961
 
This 1961 first American edition of "The Dawn and Twilight of Zoroastrianism" by R. C. Zaehner was published as a foundational entry in the G. P. Putnam History of Religion series. Written by one of Oxford's most respected twentieth-century scholars of Eastern heritage, the text serves as a thorough, deeply analytical exploration of ancient Iran's primary pre-Islamic faith. The book avoids dry summaries, opting instead to unpack the socio-political struggles, theological evolutions, and cultural clashes that shaped the Near East for centuries.
 
The structural breakdown splits the narrative into two distinct historical phases. The first half details the "Dawn" of the faith, centering on the prophet Zoroaster and examining how his message of a single, moral God managed to survive and take root within a heavily traditional, polytheistic Persian society. The second half, "Twilight," shifts centuries forward to the rise and eventual stagnation of the Sasanian Empire, where the religion became deeply intertwined with state politics before its eventual decline. Throughout the chapters, Zaehner provides clear overviews of complex concepts like dualism, cosmic battles between good and evil, and ritual purity laws, while explicitly tracking how these ideas ultimately influenced the foundational structures of Judaism, Christianity, and Islam.