From English WikiNoah
Sefer Zadok is the name of a Sadducean text, containing the doctrines of the Sadducees, allegedly being written by their founder, Zadok. No copies of this text are extant today, except for quotes in the polemics of Rabbinic and Karaite Jewish scholars of that time period.
The Sefer Zadok is also referred to in texts by Josephus and in the Talmud as a text containing the doctrines and beliefs of Sadducee Judaism. There are many stories, anecdotes, and religious and political ideas attributed to the Sadducees in these texts. These works were, however, produced by those who stood in opposition to the Sadducees (primarily the Pharisees) and are thus suspect. Little else is known about this text and those who followed its teachings.
See also: Sadducees