I & II Samuel was original one book in the original Hebrew Scriptures called Shemu'el. I will use the name Shemu'el
because it is the true title and true name of the principal character. It begins with a woman called Hannah who is looked on with disdain because of being childless. The Creator answers her prayer for a
child and when the boy Shemu'el is weened, she keeps her promise to give him over to the service of Yahuwah by taking him to Eli the Priest. Shemu'el grows, and though he had never heard the reading of the Word of Scripture, he begins hearing the Word of the Almighty from the Almighty Himself pronouncing judgement on the house of Eli.
Shemu'el pointed to the Creator as Yisrael's sovereign, but the people wanted a
king like all the other nations. Despite Shemu'el's warning that a king would collect taxes and draft their sons into military service, the people insisted so he anointed a man named Shaul who was out looking for his father's donkeys. Sha'ul was a very tall man, head and shoulders above the rest. He soon became popular, but had a tendency to be impatient and overstep his bounds in spiritual matters culminating in the Shemu'el's search for a new king under the direction of Yah.
The new king that Shemu'el found was a shepherd boy, the youngest of the house of Yishai (Eng., Jesse) of the tribe of Yehudah (Eng., Judah). His name was Dawid (Eng., David). Because of his ability to make soothing music, he was called on to comfort the king Shaul and became best friends with Shaul's son Yohanathan (Eng., Jonathan). After Dawid slew the giant Goliath, Shaul became jealous and it got very dangerous for Dawid, so he ran off. Though Shaul and Dawid were at war, Dawid and Yohanathan remained best friends until Yohanathan and Shaul died in battle against the Philistines at which point Dawid took in Mephibosheth, the Yohanathan's son who was crippled from a young age.
At first Dawid ruled well and his music ministry in the Tabernacle with his assigned singers brought a wonderful beauty to the worship of Yah. However, overcome by temptation to have the wife of Uriah the Hittite soldier loyal to the king lead to Dawid's order to have Uriah placed on the front of battle and deserted ended in Uriah's death, and Nathan the prophet pronouncing judgment on the house of Dawid saying that not only the death of the baby born of the union of Dawid and Uriah's wife Bathsheba would die, but that Dawid would experience strife in his household until the day of his death; which actually occurred. Although Dawid drew up the architectual plans for a permanent Temple in Yerushalayim (Jerusalem), because of the blood on Dawid's hands, Yah would not let him build it, but his son and successor Shlomo (Solomon) who was his second son by Bathsheba would later build it as you will see in the book of Kings (Melachim). Click on the relevant link to go there.