The Books of Samuel (1 Samuel and 2 Samuel) form part of the history of Israel in Nevi’im called the “Deuteronomistic history”, a series of books (Joshua, Judges, Samuel and Kings) that make up the religious history of the Israelites and try to explain God’s law for Israel under the guidance of the prophets. According to Jewish tradition, Samuel wrote the book, with additions by the prophets Gad and Nathan.
Samuel begins with the prophet Samuel’s birth and God’s call to him as a boy. The story of the Ark of the Covenant that follows tells of Israel’s oppression by the Philistines, which brought about Samuel’s anointing of Saul as Israel’s first king. But Saul proved unworthy and God’s choice turned to David, who defeated Israel’s enemies and brought the Ark to Jerusalem. God then promised David and his successors an everlasting dynasty.
1 and 2 Samuel were originally and, in some Jewish bibles, still are a single book, but the first Greek translation, called “Septuagint” and produced around the second century BCE, divided it into two; this was adopted by the Latin translations used in the early Christian church of the West, and adopted into Jewish TaNaCh around the early 16th century.