There are a few things which you should know about Aleister Crowley. Very briefly, he was a bisexual English occultist who hated church and tried to challenge Christianity in every way he could (like being the bottom). He talked about himself as The Gret Beast 666 and was a fond user of opioids. And he had very confusing relationships with all women. And all of this is very clear in the Moonchild. Crowley wrote many books, but most were occult texts regarding Thelema, his occult philosophy. Moonchild is the odd one out, and it is the only story novel he wrote. It monitors spiritual battles of Order and Lodge with the goal of birthing - Moonchild, supreme being with the spiritual power of the moon.
It is not a book for everyone, and several Crowley comments about the main character - Lisa, are very misogynistic. Crowley just keeps on throwing dirt on her. Also, if you disregard all occult, it can be read like a story about kidnapping, isolating and drugging poor mentally ill (probably schizophrenic) Lisa.
But Aleister Crowley could write genuinely well. It is a real page-turner, Crowley is snarky as hell and he can build layers of meaning in each sentence. He can be very serious, turning it into absurd in a moment and going bad into extreme all in one scene. The book is full of mesmerising ideas and very cinematic ritual practices. It is full of comedy too, sometimes a little bit brutal, but comedy nevertheless.
I'm pretty sure Crowley was a horrible person and an insufferable snob full of himself. But Moonchild is a really good book.