The Song of Shabbos is a sefer, not a book, that presents an in-depth understanding of the tefillos and zemiros of Shabbos, arranged chronologically, from sunset to sunset. The various treatises present the secrets and sanctity of Shabbos in a new light.
This light, the light of the ohr ha’ganuz (the hidden light) was originally revealed in the sifrei Maharal. After centuries of neglect, it was rekindled for the Torah world by the appearance of the famous maamarim of Hagaon Harav Yitzchak Hutner, zt”l, and recorded in his sefarim, Pachad Yitzchak.