A History of the Jewish Experience, by Leo Trepp (2001)
Jewish kabbalists, mystics, hold two vigils during the year, namely, the night of Hoshanah Rabbah and of Shavuot. Hoshanah Rabbah, the last half-holiday of Sukkot, was transformed by the kabbalists from a day of joy to a day of penitence, akin to Yom Kippur; they stayed awake in prayer and penitence during the night. The celebration is still observed --usually with coffee and cake; the Book of Deuteronomy is read, followed by the Book of Psalms and selections from the Zohar.
The kabbalists saw in the revelation at Sinai that took place on Shavuot the sacred marriage between the Shekhinah and Israel. The preceding night served as preparation for the "bride". On the Shavuot vigil the first and last paragraphs of the books of the Tanakh and of the tractates of the Mishnah are read, followed by excerpts from Sefer Yetzirah. The concluding prayer for both vigils condenses the teachings of Lurian Kabbalah.