Leviticus is the 3rd book of the Old Testament and the 3rd book of the Law. It has 27 chapters. In the Hebrew Bible, Leviticus is part of the תּוֹרָה (Torah, or Law).
Leviticus was written during Israel's journey from Egypt to the Promised Land, approximately one year after the Exodus. Thus, assuming that the Exodus took place in 1445 BC, as Dr. Paul Benware writes, Leviticus was written around 1444 BC.