noun
middle volume; second volume (of three)
Refers specifically to the middle book in a three-volume set. Contrasts with 上巻 (first volume) and 下巻 (last volume).
この小説は上巻・中巻・下巻の三部構成です。
This novel is a three-part work consisting of a first volume, a middle volume, and a last volume.
中巻だけ先に読んでしまった。
I ended up reading only the middle volume first.