The first two kings, Saul and David, feature prominently in the first book of Samuel.
The First Book of Samuel is the ninth book in the Bible. It tells us about the prophet Samuel and the transition of Israel from the rule of Judges to that of Kings.
I Samuel 27:1-2
"And David said in his heart, I shall now perish one day by the hand of Saul: there is nothing better for me than that I should speedily escape into the land of the Philistines; and Saul shall despair of me, to seek me any more in any coast of Israel: so shall I escape out of his hand. And David arose, and he passed over with the six hundred men that were with him unto Achish, the son of Maoch, king of Gath"