Nadab continued after his father Jeroboam to reign over the northern kingdom of Israel for two years. His reign began from the second year of Asa king of Judah (14:20b; 15:25).
Nadab did evil in the sight of Jehovah and walked in the way of his father and in his sin by which he caused Israel to sin (v. 26).
In the third year of Asa king of Judah, Baasha conspired against Nadab, killed him and all the house of Jeroboam his father, and usurped the throne (vv. 27-31). The record of Nadab thus concludes with rebellion, conspiracy, murder, and usurpation of the throne.
In 15:32—16:7 we have an account of the reign of Baasha over Israel.
Baasha began to reign over Israel in the third year of Asa king of Judah and reigned for twenty-four years (15:33).
Baasha also did evil in the sight of Jehovah and walked in the way of Jeroboam and in his sin by which he caused Israel to sin (v. 34).
The prophet Jehu came to rebuke Baasha and told him that God would sweep up after Baasha and after his house, making his house like the house of Jeroboam because of his walking in the way of Jeroboam, causing God's people to sin and provoking God to anger, and because he had killed all the house of Jeroboam (16:1-7).