Nearly everything survives by accident of geography. Egyptian settlements lay on the floodplain, were rebuilt over, and now lie under cultivation, silt or water. Tombs and temples were placed on the desert margin, where mudbrick, papyrus, wood and painted plaster last. The result is a record dominated by the dead and by the monumental, and a corresponding risk of describing a religion of funerals when most Egyptians spent most of their lives doing something else.
The principal funerary sources form a rough sequence. The Pyramid Texts, carved in royal burial chambers from the late Old Kingdom, are the oldest substantial religious writings from Egypt. The Coffin Texts of the Middle Kingdom extend comparable material to officials and their families. From the New Kingdom the compilation conventionally called the Book of the Dead, whose Egyptian title means roughly going forth by day, was written on papyrus and bought in varying quality, sometimes with the buyer's name left to be filled in later.
None of these is a doctrinal statement. They are working texts meant to be effective for their owner, and they contradict one another freely on questions that a systematic theology would have had to settle.
Other evidence pulls against the funerary bias. The workmen's village at Deir el-Medina yielded letters, oracle questions, votive stelae and ostraca showing household gods, ancestor cult and personal appeals of a kind the temple record barely mentions. Greek and Roman writers described Egyptian practice from outside and are useful but unreliable. Almost all of the Egyptian material became readable only after 1822, when Champollion established the mixed phonetic and semantic working of the script, and readings of individual texts are still being revised.