In 1 Kings 14:19 the writer points the reader to another source of information concerning the life of Jeroboam. We do not have this source any longer, and it is not to be confused with the book of Chronicles in the Bible.
The noteworthy point is that the writer of 1 Kings does not consider this information important enough to be contained in his narrative, even though it may cover more time and include more events. Indeed, they are events that worldly wisdom might consider more important than the events he selected.
1 Kings 14:20 is written in a language that is something of a stock form of writing. We have seen it before in the case of Solomon, and we will see it again in the case of later kings. As a method of indicating that the writer’s concern with a king is finished, he mentions the length of his reign and the fact that he died. The method of expressing the latter information is to say he slept with his fathers. Such is true whether the king is evaluated as righteous or evil.
19 Now the rest of the acts of Jeroboam, how he warred and how he reigned, behold, they are written in the Book of the Chronicles of the Kings of Israel.