John Gill Commentary 2 Kings 15:21

"Now the rest of the acts of Menahem, and all that he did, are they not written in the book of the chronicles of the kings of Israel?" — 2 Kings 15:21 (ASV)

And the rest of the acts of Menahem
We are referred to the same book of chronicles for them as for those of the rest of the kings, which seems to be a form the historian uses of them all.