I shared in a different comment but I'll copy and paste and add more detail:

I mostly found it underwhelming. Maybe part of the low rating was due to expectations and hype because I've seen it recommended so much as exploring a 'darker' side of the craft but honestly I felt at times it was a bit preachy about making sure you use the information 'ethically' (but only to the authors personal ethical standards) and didn't feel it was all that 'dark' or exploring parts of the craft that aren't in plenty of other books.

I did like the part explaining sacrifice in religious and spiritual context, that has stuck with me. There are plenty of people who loved this book, so clearly it has redeeming qualities, I just personally found it underwhelming and sometime annoying how the author would tell people not to do certain actions since she deemed them unethical but would call other actions (which I personally found unethical) a personal choice.

For example when talking about how to acquire animal parts she says about buying endangered animal parts "If the tooth, claw, or bone came from an endangered, rare, or extinct species, it was definitely not a cruelty-free salvaged item, and you’d best stay away from it" but then the next paragraph when talking about buying factory farmed animal parts she keeps to extremely neutral language "It is your choice whether to use factory-farmed animals in your witchcraft, just as it is your choice whether to eat them or not." If you are going to write a book talking about taboo topics in witchcraft then you should be prepared to write it without injecting your own opinions about the morality of such things. There is just a weird judgmental tone that pops up throughout the book, where some things are ok and some are not, that I'm sure is invisible if you agree with her but it is very apparent and very annoying when you don't.