The Aten was not completely new - his family had had some interest in the Aten.
Also I have memories of there being a burial of an Aten priest at Saqqara inthe Remeside period.

Tutness has a point-you do have to look at it from both sides, from Akhenaten's point of view and from the Priests of Amun's....It seems, from newer books and such, that most are tending to lean toward Akhenaten doing all the "reforms" because of political reasons, which others have already mentioned, but I think it went beyond that. Some scholars used to say that he was mentally unstable....(Which totally erks me.) Then, you've got scholars like Weigall who say that it was purely religious. I, myself, say it was both. His "reforms" killed two birds with one stone in a way. He's following his own beliefs, but at the same time he's cutting down the threat of the Amun priesthood. (I back Akhenaten in the view that they had WAY too much power. When a temple to a god owns about a third or more of the country...yeah, it's time to do something, and who better to do that than a Pharaoh who had religious convictions as well?)

Against his actions being politicaly motivated is the way he seems to have let the empire go.

He seems to have been more than willing to let the dailey operations of the Empire to be handled byt others, and to have spent most of his time thinking of, and gradising, the Aten.
We will probably never know, as I have stated above, the real reasons he had for the various actions he took. Was it completely political? Completely religious? I pweaonally think it was a combination of both, a relious fevor and some very astute advisors.
That Amun had grown too powerful was quite obvious. Curtailing that power needed to be taken in small steps. And changing the outlook of thee common person to a religion that emphasized one god was impossible. The old religion was so very entrenched in the lives of those peoples. Even in the city of Aten, evidence of the continued worship of the old gods has been found.

Osiris got a point....Evidence for the worship of the old gods was found in Akhetaten....Bes, Tawaeret.....The olds gods that the common people prayed to and depended on...The old religion was embedded in these people like Osiris said...And we will probably never know exactly what his motivations were, like just about everyone else has said.....But I've always thought he was ahead of his time even if he did "ignore" his daily duties as Pharaoh, and that there had to be some religious convictions. Why else would he risk his people hating him and destroying his images and afterlife if it wasn't for something that he believed in strongly? It wouldn't make any sense. He was Egyptian. Afterlife=EVERYTHING

I think it is notable that he promoted the sun as other solar deities (like tefnut) remained in favour. Amun developed from the ogdoad of heliopolis while the solar aspect of ennead of heliopolis is present in the Aten.

It is tempting to simplify and say that you have a choice between naturalistic visible gods (the sun, the river etc) who are popular with Akhenaten and also the common people and the invisible gods (Amun is after all "the hidden one") who represent ideas (wisdom, truth etc). Although the two were inextricably merged over time, you can see why a king who was naturally drawn to nature (as shown by art works and his own poetry) would adopt the main alternative to Amun - the sun.

Thus, i sit on the fence. I think he was an intellectual/religious man who loved to spend time with his family and in contemplating nature. But he was also egotistical or sensible enough to want total control and to be free of the priests of Amun who had massive grants of land and very cushy tax deals. Retaking that land and its revenue would have easily paid for his new city.

I don't know that he was really a peace-lover. By abandoning Egypt's allies the Mitanni and allowing the Hittites to rampage around the area he was hardly promoting peace. He does not seem to have attempted any diplomacy to prevent the situation degenerating. It seems he was only really interested in his comfy life, or am I being too harsh?