Ancient Egyptian religion sprang from a worldview wildly different from ours, and it does not match Western preconceptions of what a religion is, or what priests are, or what myths are. Therefore, a lot of Egyptological writing about religion spends a long time on what can feel like tiresome hemming and hawing: agonizing over definitions and dispelling preconceptions. It's necessary, but it's rarely pleasant or interesting to read. This is an entire book dedicated to the hemming and hawing. On the topics of temples, festivals, myth, ethics, and funerary customs, Quirke describes a litany of barriers to our understanding of so alien a culture.
As an example, no texts from before the middle of the New Kingdom tell myths as cohesive stories, and even after that point such stories are rare. Thus, for about half of the history of ancient Egyptian religion we have only brief references to the same mythic events that later show up in cohesive narratives. Egyptologists often assume that coherent myths were passed down orally even if they weren't written down, but Quirke points to anthropological research that has shown how much of the human learning process depends on non-verbal instruction, and he suggests that the brief bits of myth that we find in sources like funerary texts may have been passed down by some process like this. How might that have worked in practice? Quirke doesn't say; he just says Egyptologists should study the possibility.
This is my biggest frustration with the book. There are very few conclusions, only problems and possible avenues for future study. Quirke does make some valuable points. For instance, he emphasizes Egyptian burials that don't fit the standard Egyptological description of Egyptian funerary customs, and he points out that Egyptologists' reluctance to translate the word maat (which he renders as "what is right") makes ancient Egypt seem somehow apart from every other human culture, all of which have concepts of right and wrong. But, overall, this book feels very unsatisfying. People seriously studying ancient Egyptian religion should probably have it on hand, as a constant reminder of how our preconceptions get in the way of understanding a strange society, but it works better in giving future Egyptologists a jumping-off point than in informing people about ancient Egyptian religion.