休(やす)みの日(ひ)は家(いえ)で本(ほん)を読(よ)みます。

This phrase describes a typical activity during leisure time. "休みの日" (yasumi no hi) refers to "days off" or "holidays." "家で" (ie de) indicates the location of the action, "at home," while "本を読みます" (hon o yomimasu) means "read books."

休日によくする活動について話す時に使います。「〜で」は行動の場所を示す助詞です。