State religion in the New Kingdom centered on Amun-Ra, a fusion of the originally local Theban god Amun with the ancient solar god Ra, worshipped at the vast Karnak temple complex, whose priesthood accumulated land, gold and political influence on a scale that made it a rival to royal authority by the dynasty's end. Karnak's halls and pylons were extended by successive kings across the whole period, and its annual Opet Festival, in which Amun's image traveled by river to Luxor Temple, was among the empire's great state occasions.
The Book of the Dead, more properly the Book of Going Forth by Day, became the standard funerary text of the period, a further evolution of the Old Kingdom's Pyramid Texts and the Middle Kingdom's Coffin Texts, now written on papyrus scrolls that could be purchased, partly personalized and placed in the coffin of anyone who could afford a copy, including the celebrated judgment scene in which the deceased's heart is weighed against the feather of Maat. Akhenaten's Atenist reform stands against this mainstream as a deliberate rupture, replacing the entire pantheon and its afterlife literature with a solar theology focused on light itself rather than a personified sun god, and its abrupt reversal after his death illustrates how firmly Amun's cult, the empire's wealth and the Book of the Dead's promises had become fixed in New Kingdom religious life. Miriam Lichtheim's translations of New Kingdom literature and the Oxford Encyclopedia of Ancient Egypt, edited by Donald Redford, remain standard references for the period's texts and theology.