Hey Gseg, the best introduction to atheistic/modern Satanism is the Satanic bible by Anton LaVey, once you read it you'll know if you're a Satanist or not. You could pick it up on eBay or something 2nd hand for cheap. You'll either read it and be appalled by the virulent nihilism and it's endorsement of animalistic code of conduct. On the other hand, it will change your life forever and you'll know you always thought that way or wanted to think that way. The difference between Atheism & Satanism is that atheism is imbued with humanistic morals and virtues. Satanism is all about the self and your own personal power. I hope that I have been helpful to your queries.