The chronology of the early books cannot be taken as it stands. The Nihon Shoki dates the accession of Jimmu, the first sovereign, to 660 BCE, and gives the early emperors reigns and lifespans of well over a hundred years. The standard explanation is that the founding date was chosen for its position in the sexagenary cycle: 660 BCE falls 1,260 years, twenty-one cycles of sixty, before 601 CE, a year that continental prognostication marked as one of great revolution. Having fixed that starting point, the compilers had to fill the gap, and the early reigns were stretched and sovereigns probably added to cover it. Eight early emperors carry names and genealogies but no events at all, and are widely regarded as later insertions. The chronicle becomes reasonably reliable only from the fifth or sixth century, and firm from the seventh.
None of that reduced its standing at court. The Nihon Shoki, not the Kojiki, was the text the aristocracy studied. Formal lecture series on it were convened at the imperial court, six of them across the Heian period, running for years at a time and concluding in banquets at which courtiers composed poems on the deities and heroes of the text. Later chronicles were commissioned to continue it, producing the sequence known as the six national histories.
Its later career ran with the Kojiki's. It supplied the same imperial descent narrative to State Shinto and to nationalist teaching until 1945, and is now read as a compiled historical source whose value lies in what it recorded, and in what it shows about the recording.