Properly, the inner bark of the papyrus plant, i.e. (by implication) a sheet or scroll of writing -- book.

βίβλος (biblos) − 1 Occurrence

βίβλου (biblou) − 1 Occurrence

βίβλους (biblous) − 1 Occurrence

βίβλῳ (biblō) − 7 Occurrences