So. Here's the thing about witchcraft that none of these "how to become a modern witch"-author-wants-to-make-a-quick-buck books tell you.
Saying "I want to be a witch/use witchcraft" is the same as saying "I want to be a cyclist/learn to ride". It's a legit thing to want to do! But here's the thing -- you can't do it without a bicycle.
Witchcraft isn't a religion. Witchcraft, like prayer, is a tool that is used largely in nature-based religions (although not exclusively). It needs to be placed within a specific framework for it to be taught or learned. Your framework is your bike.
I'm not saying that said framework needs to be tied to a God or pantheon; witchcraft without the belief in gods exists, albeit rarely, and it is valid. Every witch to their own. (Your bike can be yellow or blue or an ungodly mess of purple polka dots, it'll still work.)
The thing about "how to witch" books is that they don't define what witchcraft is. They let you believe in a nebulous sort of ability that you can learn and then use to make people fall in love with you/have that bitch at the office get her comeuppance/win the lotto. Which makes about as much sense as letting someone think cycling is just a special way of moving.
Look, theistic or not, one fundamental thing you have to believe, at least a tiny bit, to perform witchcraft -- the manipulation of living "energy" (I know, I know, science buffs -- don't hate me for using that word! I'm hard on the lookout to find one that works) to bring about a desired result in reality -- is that said energy is there in the first place, and that the ability to manipulate it is actually possible.
If you don't believe that, then you can't do witchcraft. Not because you're lesser or not cool enough or whatever, but because you're lacking the fundamentals. If you don't have a bike, you can't be a cyclist. That's the end of it. It's not even if you don't have a Tour de France level sports cycle, if you don't have have so much as a second-hand bike that was rescued from the local tip...you can't become a cyclist. No matter how much you want to.
If you don't believe there's energy to be manipulated, you can't do witchcraft. End of story. No matter how cool it currently is to call yourself a witch.