They may be "atheolatrial", so to speak, but the existence of deities is not explicitly denied beyond the sense that the permanence and independent reality of anything within samsara is refuted. The "ultimate reality" may be impersonal, but that, if anything, fits with the concept of the divine that many in the present day have when they say the word "God". Few, if any, people these days picture God as a hoary, bearded old man sitting on a cloud and frowning (or smiling, take your pick) down at Creation.

The figure of Christ is actually strikingly similar to the figure of the Buddha. Both offer a way to salvation/enlightenment that involves a renunciation of material attachments, just acts and behavior and a reinterpretation of spiritual reality that makes the old temple cults obsolete and worthless. Both are universalist creeds that grew out of narrow ethno-religious traditions, and both influenced those narrow traditions and forced them to evolve to remain marginally relevant in modern society (though both are essentially relics of a bygone era).

I think that any reading you do on Akhenaten will disappoint you. His "monotheism" was really closer to the "national deity" concept that was present in the Near East in the Iron Age, where a polytheistic world was assumed but one god assumed primacy and was worshipped almost exclusively. The concept is similar to, but not exactly, henotheism. The development was what we would today call "political", though obviously in ancient Egypt the ideas of separate "religious" and "political" spheres would be an alien concept. The temples had grown powerful, and Akhenaten sought to wreck their power and consolidate the state cult around himself as the living expression of his prime deity, the Aten (probably actually a-t:'n based on Amarna transcriptions in Akkadian, the whole name almost certainly pronounced i:x-na-a-ti:'n, though in correspondence he is referred to by his Horus name, spelled "mery-aten" but in Amarna letters mai-ati:'n). It was sort of like the destruction of the monasteries in Reformation England combined with the Stalinist cult of personality, and very, very light on the philosophy from the extant records.