First Samuel chronicles the events that took place between the time of Samuel the prophet's birth and the death of King Saul, the first anointed ruler of Israel. It also covers the rise of David, Israel's greatest king.
Originally published along with Second Samuel the accounts in First Samuel were probably recorded by Samuel and later added onto by the prophets Nathan and Gad. Parts of First Samuel were written near time when the Ark of the Covenant was captured by the Philistines, as the author makes an effort t note that it was in the Israelite's possesion
Samuel would have written the first twenty-four chapters of the book which documents his own life along with that of Saul and David. Since the rest of the book takes place after the death of Samuel  Samuel could not have written them, so other authors would have had to add to it. The prophets Gad and Nathan were contemporaries of David, making them the most likely candidates for accounts after Samuel's death. Gad was the successor to Samuel as a seer, and Nathan served as the prophetic advisor to David.
Whether or not Samuel wrote any portion of the book himself or not, it is clear that its writers utilized material written by Samuel, Gad and Nathan. In fact, it is possible that "Samuel's records" referred to by the Chronicler could be a reference to the Book of First Samuel or that First Samuel was part of those records. The records of Samuel may have included judicial hearings recorded in 1st Samuel, priestly records about his service of dedication, and other life events.
If the book was not written by Samuel, it is appropriate that it has been named for him because of his involvement in the book's accounts and his legacy afterwards. Since the Second Book of Samuel was once in the same volume as First Samuel, it came to be named after Samuel to reflect the continuity of the two books.
First Samuel is obviously an historical account. The book documents the events of Israel under an early monarchy, covering the lives of the early kings and multiple battles. The work contains very descriptive accounts about a period of Israel's history in great detail, most of which are only documented in this book.
Much of the material is straight reporting of the events from a third person point of view. There are also stretches of dialogue indicating either eyewitness records or divine guidance in reconstructing what was said. In including such detail, the editors and writers enhance the details, give accuracy, and record important decrees and commands which affect later events.
There is only one piece of poetry within the entire book. Roughly a third of the second chapter includes the prayer of Hannah to God when she dedicates her son Samuel. The prayer is very poetic, including much worship and praise of Yahweh. The style of the prayer is an early example of the style of prayer common at the time, the same sort of style used in the Book of Psalms. It is not unlikely that her prayer was a pre-written recitation used in praising God.
I. The Closing Days of the Judges
- A. The Judgeship of Eli (1:1-4:22)
- B. The Judgeship of Samuel (5:1-8:22)
II. United Israel under Monarch
- A. The ascendancy of Saul (9:1-15:35)
- 1. Chosen as King (9:1-12:25)
- 2. National victories and Personal failures (13:1-15:35)
- B. The Conflict of Saul and David
- 1. David's Rise to fame (16:1-17:58)
- 2. Saul's controversy with David (18:1-31:13)