Title, Date, and Author:

I and II Samuel are named after the person God used to establish a monarchy in Israel. Samuel not only anointed both Saul and David, Israel’s first two kings, but he also gave definition to the new order of God’s rule over Israel. Samuel’s role as God’s representative in this period of Israel’s history is close to that of Moses (see Psalm 99:6; Jeremiah  15:1) since he, more than any other person, provided for continuity in the transition from the rule of the judges to that of the monarchy.
I and II Samuel recount the stories of Samuel, Saul, and David. Saul’s reign began sometime between 1050 to 1030 and ended in 1010. David reigned from 1010-971 BC. I and II Samuel were probably written soon after the end of the reign.
I and II Samuel were originally one book. It was divided into two parts by the translators of the Septuagint (the pre-Christian Greek translation of the OT)—a division subsequently followed by Jerome (in the Latin Vulgate) and by modern versions. The title of the book has varied from time to time, having been designated “The First and Second Books of Kingdoms” (Septuagint), “First and Second Kings” (Vulgate), and “First and Second Samuel” (Hebrew tradition and most modern versions).
The author of I Samuel is not known since the book itself gives no indication of his identity. Whoever he was, he doubtless had access to records of the life and times of Samuel, Saul, and David. (From NIV and ESV Study Bible)

Historical Setting and Context:

The majority of the action recorded in I and I Samuel took place in and around the central highlands in the land of Israel. The major cities of I Samuel are to be found in these central highlands: Shiloh, the residence of Eli and the tabernacle; Ramah, the hometown of Samuel; Gibeah, the headquarters of Saul; Bethlehem, the birthplace of David; Hebron, David’s capital when he ruled over Judah; and Jerusalem, the ultimate “city of David.”
The events of I and II Samuel took place between 1105 B.C. (birth of Samuel), through King David’s reign in 971 B.C., covering about 135 years of history. During those years, Israel was transformed from a loosely knit group of tribes under “judges” to a united nation under the reign of a centralized monarchy.
As I Samuel begins, Israel was at a low point spiritually. The priesthood was corrupt (I Samuel 2:12-17, 22-26) the ark of the covenant was not at the tabernacle (I Samuel 4:3-7:2), idolatry was practiced (7:3-4), and the judges were dishonest (8:2-3). Through the influence of Samuel and David, these conditions were reversed.
During the years narrated in I and II Samuel, the great empires of the ancient world were in a state of weakness. Neither Egypt nor the Mesopotamian powers, Babylon and Assyria, were threats to Israel at that time. The two nations most hostile to the Israelites were the Philistines and the Ammonites.
The Ammonites were descendants of Lot (Genesis 19:38) who lived on the Transjordan Plateau. The major contingent of the Philistines had migrated from the Aegean Islands and Asia Minor in the 12th century B.C. The Philistines controlled the use of iron, which gave them a decided military and economic advantage over Israel (13:19-22). II Samuel records the conquest of both the Philistines and the Ammonites. David conquered the Philistines (II Samuel 8:1) and the Ammonites (II Samuel 12:29-31), along with other nations that surrounded Israel (II Samuel 8:2-14).
(From Insights for Living and MacArthur Study Bible)

Eugene Peterson Summary:

Four lives dominate I and II Samuel: Hannah’s, Samuel’s, Saul’s, and David’s. These are large lives—large because they live in the largeness of God. Not one of them can be accounted for in terms of cultural conditions or psychological dynamics; God is the country in which they live.
The stories of these lives are not exemplary in the sense that we are meant to stand back and admire them, knowing that we will never be able to live either that gloriously or that tragically ourselves. Rather, they are immersions into the actual business of living itself: This is what it means to be human. These four stories do not show us how we should live but how in fact we do live, authenticating the reality of our daily experience as the stuff that God uses to work out His purposes of salvation in us and in the world.
There is surprisingly little explicit God talk here—whole pages sometimes without the name of God appearing. But God is the commanding and accompanying presence who provides both plot and texture to every sentence. This cluster of interlocking stories trains us in perceptions of ourselves, our sheer and irreducible humanity, that cannot be reduced to personal feelings or ideas, or circumstances. If we want a life other than mere biology, we must deal with God. There is no alternate way.”
One of many welcome consequences of learning to “read” our lives in the lives of Hannah, Samuel, Saul, and David is a sense of affirmation and freedom: We don’t have to fit into prefabricated moral or mental, or religious boxes before we are admitted into the company of God—we are taken seriously just as we are and given a place in his story. For it is, after all, his story; none of us is the leading character in the story of our life.
We do violence to the biblical revelation when we “use” it for what we can get out of it or what we think will provide color and spice to our otherwise bland lives. That results in a kind of “boutique spirituality”—God as decoration, God as an enhancement. The Samuel narrative will not allow that. As we submit our lives to what we read, we find that we are not being led to see God in our stories but to see our stories in God’s. God is the larger context and plot in which our stories find themselves.