I read it as a paperback somewhere around 1990, might be a bit older. It's set on Earth in approximately contemporary time (I don't remember the time frame, but there were cars and phones. I don't think there were cell phones). It had a Caucasian male on the front cover, I think with a flame in the palm of his hands. The cover was largely whites and greys, maybe with him standing in front of a marble wall with some symbols on it? There was white magic and black magic with corresponding "lodges" (something I think is intended to parallel the Crowley hermetic magic) and, I think, something with different schools of "elemental" magic. I want to say that the good and evil aspects of the school were the reverse of what one might expect with black magic being creative and white magic being destructive.
The plot is a bit of a mash in my head as well. The protagonist was trying to investigate something, possibly a missing friend. To do so, he had to infiltrate the "evil" lodge, which at some point necessitated him signing a contract in blood. He tries to weasel out of it by signing a different name, but eventually gets called on it, something about how the false name he signed was his real name in his heart. Somewhere amidst it all, I remember him driving out into the desert. For some reason, that stuck in my head.
Only other "detail" I can recall is that I think that the title of it involved "The Eye of" at the beginning of it.
Just to rule out a few possibilities, I've read some excerpts of Crowley's Moonchild and that's not it. And, despite the similar mention of lodges, it's not a Twin Peaks adaptation. And I'm 99% certain it was none of the Mercedes Lackey books involving hermetic magic.