Well written historical Christian fiction suitable also for Judaism
The story is very true to the Old Testament accounts, and as David is the ancestor of Messiah, whether you believe, as Christians do, that Messiah has come once (as the suffering servant in Isaiah) and will return as the conquering Head of the Lord's army, or you believe, as non-Messianic Jewish people believe, that Messiah has not yet come to earth, the story still has merit and is part of the heritage of both the Jewish people and of Christians.
The book begins with Jesse and his sons standing with Samuel, judge and prophet (or seer, as he is called in the book), as the last bits of a peace offering that Samuel has called for are burning into ash. The meat has been taken ahead to the feast. Once all but Jesse and his sons - save one who is tending sheep - are alone with Samuel, Samuel tells them why he has come. He says each of Jesse's sons is to pass before him to see which one will be anointed.
The problem is, although Samual sees a lot of potential, especially with the 3 oldest - all of whom are already in the army and are experienced warriors, and know their way around the royal court, God rejects them all. Still others have skills in negotiations, in business, in dealing with people of other cultures and countries. Still, God rejects them. All of them are frustrated, especially, I'd imagine, Samuel, who had told Jesse to bring all of his sons, only to find the youngest one is up in the hills, tending sheep. Once David returns, God selects him, and before he knows what is happening, David finds himself with anointing oil all over his head and face, and a warning is issued that God is displeased with Saul's disobedience, more so since Saul refuses to repent in his heart. David is told he will succeed Saul on his death - which is not in the OT anywhere I can see, but David waited until Saul's death, didn't facilitate or cause it directly or indirectly, and he only asceanded the throne after Saul died, as Saul's God-chosen, God-anointed successor. Perhaps Samuel did tell him...perhaps the Spirit of the Lord did...perhaps both.
Samuel swears them to secrecy, but they don't need convincing. When kings are threatened, and especially when they were anointed, disobedient, refuse to repent, have God's Spirit taken from them, and feel threatened, the normal practice in other countries was for the sitting king to wipe out the "usurper" and their entire family. The risk this will happen now is high, because when David was anointed, the Spirit of God left Saul and came upon David, something Saul would know, Saul is now vulnerable to demonic oppression and even possession.
When he was young, David had learned the basics of playing their harp, plus, like all boys, had been drilled in the arts of war. When he was alone, once he had the sheep safely in a pasture with still water from which to drink (sheep can drown in running water), the job could get pretty boring. Helpers doubtless practiced their battle skills and their weapons moves, as well as hand-to-hand combat moves, even when alone. Since a sling was an often used weapon, and David was good with it, he likely found things to use for tatgets. And when he was in a state where his practice was complete for the time being, he composed songs as well as singing ones that were familiar. He sought the Lord in his singing and playing. He
God started training the young heir. The book details hit specifically battling a lion and a bear, and the Spirit delivering him by giving him the strength and cunning to fight them and win. These were predators likely known to all shepherds at the time. The Bible, however, only mentions David telling Saul, when he volunteered to fight Goliath, that as a shepherd, he had killed a lion and a bear, no details given.
One part of the Bible says Jesse had 7 sons, another says he had 8. To explain this, the author creates a brother who defies God, and his country, and tells the secret of David's anointing, then defects to the Philistines, because this would have gotten his name blotted out from the genealogy of the family and accounted for the different numbers. There are also tales of him trying to bust a Philistine spy ring that I don't see in the Bible. This happens after someone tells King Saul about a young shepherd with a beautiful voice, whose music may be able to keep the fits, black moods, etc., at bay. When David is in court, the Spirit in him, and thus on his music, does indeed do just that. Then, when the King's life's os threatened, David saves him. Meanwhile, the friendship between David and the king's eldest son deepens until they are like brothers. David is made armor bearer to the King, butbthen is left back in Bethlehem when the armies go to fight. He is with the sheep to free up those brothers not in the army to provision the armies. One day, Jesse sends David to deliver items to his brothers, at which time he fights Goliath and wins. The rest of the story is in a 2nd book.