On the 5th of Tevet (Hei Teves) in 1987, the extensive library of the sixth Rebbe, Rabbi Yosef Yitzchak Schneerson, was declared as belonging to Agudas Chasidei Chabad Lubavitch. The U.S. Federal court issued this ruling after a lengthy, highly-publicized trial. The anniversary of this event is marked annually, by purchasing new sefarim (Jewish books) and studying them. 

You can browse the Kehot Publication Society annual Hei Teves sale of up to 50% off  by clicking on the link below. 

http://store.kehotonline.com/