The Nihon Shoki, also called the Nihongi, gives two books to the age of the gods and then twenty-eight to the sovereigns, from Jimmu to the abdication of Empress Jito in 697. The later reigns are dense with datable material: edicts, embassies, appointments, omens, the arrival of Buddhism, the Taika reforms, the Jinshin succession war of 672. The format is annalistic, entries dated by reign year, month and day in the manner of a Chinese court history, and the last books read as something close to documentary record.
The chronicle's most valuable feature is editorial rather than narrative. Where traditions disagreed, the compilers did not choose. They set out a main version and then appended alternatives with a phrase conventionally translated as in one writing it says. The account of Izanagi and Izanami, of the birth of the sun deity, of the descent to earth, each arrives in several forms, sometimes as many as eleven for a single episode, differing in names, sequence and moral weight.
This is unusual for a text with an official purpose, and it makes the Nihon Shoki the richer source of the two chronicles for anyone studying how the myths varied between regions and priestly houses. The Kojiki tells one story cleanly. The Nihon Shoki shows the seams.
The two divine books, known as the volumes of the age of the gods, were treated as a distinct unit in later centuries and copied, lectured on and commented upon separately from the rest. Scattered through the whole work are more than a hundred songs, transcribed phonetically rather than translated into Chinese, which preserve early Japanese verse and language that the surrounding prose does not.