It's not a terrible book. It is essentially elements of Nietzsche, Ayn Rand and Ragnar Redbeard (very similar to Might Is Right in parts, Might Is Right being the far superior) all mangled into the one plagiarised and inconsistent book but it's still readable.
I enjoyed it more when I read it before studying philosophy. Now it is less appealing but still, worth giving it a go if you want something to keep you occupied for such a low price.
I should point out that the title is slightly misleading; it isn't Satanism in the traditional sense. It is an atheistic worldview which is largely rejected by theistic Satanists, though does bear some similarities. Like I said before, it is mostly a rip-off of philosophers who LaVey clearly admired, but can work as a kind of introduction to them.