Only one book in the Hebrew Bible is generally classified as apocalyptic literature, and that is the book of Daniel. But that is not to say that Daniel is the only book that shows characteristics typical of apocalyptic literature. Certain motifs characteristic of apocalyptic eschatology can be found in the myths of ancient Mesopotamia. Motifs of cosmic warfare pervade mythic material, such as the battle between the high gods and the sea monsters. This divine warrior motif is also present in biblical apocalyptic literature.
The period 200 BC to 200 CE was a time of history-making changes in Jewish culture and religious and political philosophy. It also harbors the beginnings of the development of Christian philosophy, culture and beliefs. For these reasons events of that period still exerts considerable influence on large segments of Western philosophy and culture today. That is what makes it such an interesting period to study.
The so-called Letter of Aristeas or Letter to Philocrates  is a Hellenistic work of the second century BCE, one of the Pseudepigrapha. Josephus Flavius who rephrases some of the letter, ascribes it to Aristeas and written to Philocrates, describing the Greek translation of the Hebrew Law by seventy-two interpreters sent into Egypt from Jerusalem at the request of the librarian of Alexandria, resulting in the Septuagint translation.