There isn't one single "Jewish holy book written after the Old Testament." The Jewish tradition is rich and diverse, with several important texts that developed after the completion of what Christians refer to as the Old Testament (which Jews call the Tanakh). Here are some of the most significant:
* The Talmud: This is arguably the most important post-Tanakh text. It comprises the Mishnah (a compilation of Jewish law) and the Gemara (commentary on the Mishnah). There are two versions: the Babylonian Talmud and the Jerusalem Talmud.
* The Mishnah: As mentioned above, this is the first major written collection of Jewish oral traditions. It forms the basis of the Talmud.
* Midrash: These are collections of rabbinic interpretations and expansions of biblical stories, often used to teach moral lessons or explain difficult passages.
* The Zohar: This is a central text of Kabbalah (Jewish mysticism).
* The Siddur: This is the Jewish prayer book. While individual prayers may predate the Talmud, the compilation and standardization of the prayer book occurred over a longer period.
The Talmud is often considered the most authoritative post-biblical text, serving as a primary source of Jewish law and thought.