There isn't one book. For the Ruthenians, the Metropolitan Cantor Institute has the propers derived from the menaion in a 12 volume series. Generally, the propers are picked from either the day of the week, or the saint of the day, or a DL for the deceased. The prokeimenon and alleluia are from a common set related to the main commemoration. My guess is there is a typikon the cathedral is using to determine what is commemorated, in conjunction with the celebrant saying, "We're doing this or that".