The book itself is anonymous
2 Samuel never introduces its writer by name. It tells the story of David’s reign, from his grief over Saul and Jonathan to his final years as king, but it does not pause to say, “I, so-and-so, wrote this.” So the most careful answer is that the human author is unknown.
That needn't make the book less valuable or trustworthy. Many biblical books do not identify their writers within the text. What 2 Samuel gives us is a searching account of David, showing both God’s covenant mercy and the real damage caused by David’s sin.
Why Samuel is connected with it
Samuel is closely tied to David’s rise. He anointed David as Israel’s future king and served as a prophet and judge during the transition from Saul’s rule. Because the books of 1 and 2 Samuel bear his name, people have naturally associated him with their material.
Yet Samuel died while Saul was still king, before David became king over all Israel and long before many events recorded in 2 Samuel took place (1 Samuel 25:1). He may have preserved or contributed to earlier records, but he could not have completed 2 Samuel by himself.
Nathan and Gad may have supplied records
A later passage gives the clearest biblical clue. When it sums up David’s reign, it says that accounts of his acts were recorded in the writings connected with Samuel the seer, Nathan the prophet, and Gad the seer (1 Chronicles 29:29). Nathan appears several times in 2 Samuel, including when he confronted David after his sin with Bathsheba (2 Samuel 12:1).
This does not tell us exactly who assembled the final book. Still, it shows that recognised prophetic witnesses recorded David’s life. Many readers therefore understand 2 Samuel as a carefully compiled account that drew on records associated with these men.
Now the acts of David the king, first and last, behold, they are written in the book of Samuel the seer, and in the book of Nathan the prophet, and in the book of Gad the seer,
Read it as David’s story before God
The question of authorship is worth asking, but 2 Samuel’s main concern is larger than a byline. It shows God establishing David’s kingdom, making promises to his house, and then dealing honestly with David’s failures. David ruled in Jerusalem for thirty-three years after first ruling in Hebron, and the book follows the weighty consequences of his choices (2 Samuel 5:4-5).
As you read, watch for the prophets Nathan and Gad, and notice how often God’s word directs the story. The author may be unnamed, but the book consistently calls readers to see Israel’s king under the authority of Israel’s God.