Everything You Want To Know About Magick is not meant to be specifically Thelemic, but Thelema is non-dogmatic, meaning you can take or leave what you want from it. There is no strict formal code, other than to enjoy life the most you possibly can.
I quote from the Book of the Law, and reference Crowley in various other ways, because he not only offers concise and often poetic examples of the sometimes obtuse concepts in magick, but also because it will further introduce you to Aleister Crowley. Whether you like him or not is of no matter; he is such a lynchpin of modern occultism, one cannot be a serious magician and not be at least minimally acquainted with his work, which is voluminous, complex, and erudite. I hope what you learn in this book goes a long way to understanding and using his magick if you are so inclined.
Aleister Crowley was a big proponent of doing your own thing and thinking for yourself. So in that way, I’m entirely in agreement with him. If you get anything out of my book, it is to be that way with your entire life. Learn, study, and analyze information from many sources and make your own decisions regarding black magick, love, morals, and ethics, government, etc. Make choices that enhance your life and those you love, anything else is the only “sin” you can make.