Both books are important history books telling and describing Japanese myths compiled in the Nara Period and ancient history. They each contain only myths in the beginning part of the book and take on more characteristics of a history book as the writing approaches the era when these books were written.
However, while there is a way of thinking that some of the descriptions in the latter half of the book are still skeptical, many of the recent archaeological findings have resulted in providing more support to prove the accuracy of the descriptions in the Kiki (the description of the reconstruction of Horyu-ji Temple and Amakashi no oka Hill of the Soga clan.)
Careful assessment is required, but since the historical materials in that era are very few, they are still important as historical materials.
Until the Muromachi Period, more people collectively called the two books and "Sendai Kujihongi" (Ancient Japanese History) as 'Sanbu no honsho' (three books of origin), which were important historical books telling Japanese myths and ancient history, but "Sendai Kujihongi" was thought to be an apocryphal book in the Edo Period and after that, more people called only these two books Kiki.