Satan, as an idea and a figure, is fascinating.
If you're into religions, like I am, you might want to look into some of Farid ud'Din Attar's works about Satan.
Attar is actually a Sufi Muslim poet who believed Satan was the greatest Muslim who ever lived.
Needless to say, his thoughts were highly controversial for Orthodox Sunni and even Shi Muslims at the time.
As for Satanism the religion itself, just given my brief and short experience, Satan the figure so common in Christian traditions actually doesn't play much of a role. Now mind you, this is just from my personal experience observing a Black Mass that a colleague of mine, who was head a particular Satanist sect, invited me to.