The leaders of Lubavitch would often deliver a series of interrelated discourses, developing the full depth and breadth of their spiritual, philosophical theses.
One of the most famous, is this, a 61-part serial delivered by Rabbi Shalom Dov Ber Schneersohn, the fifth Lubavitcher Rebbe, begun on Rosh Hashana 5666 (1905) through the close of 5668 (1907). Elder Chasidim once declared that this work contained "the revelations of the light of Moshiach."
The series Yom Tov Shel Rosh Hashanah, 5666 explains many concepts and previous texts in the Torah of Chasidus. At the end, the Lubavitcher Rebbe RaShaB appended a conclusion to the series, summarizing the novel contributions to the fundamentals of Chasidic thought contained in Samech Vov.
Among his discourses, the Rebbe RaShaB spoke with special approbation of Samech Vov, for all the qualities that distinguish his discourses are there to be found in great measure, and It is known that the Lubavitcher Rebbe RaShaB connected his delivery of Samech Vov with the Ketz, the expected arrival of Moshiach, forecast in the books of earlier sages to come in that year (from a talk of the Lubavitcher Rebbe).
This emended edition includes comments and explanations by the Rabbi Yosef Y. Schneersohn and Rabbi Menachem M. Schneerson, respectively the sixth and seventh Lubavitcher Rebbes.