I think his other writing is more interesting to read, but White Stains is special in how foul it is. The fact it was written at all blows my mind.
Edit: I will add though, Crowley does have a peculiar and breathless way of writing that is noteworthy, but you'll find it in any of his works. And it's neat that he wrote White Stains both in english and in french and they are considered separate works!
Somewhat unrelated, I'm going through Liber Null, from Pter J Caroll and I find it pretty solid, did you ever read it? It's not Thelema but it's prett close.
Personally, I think Book 4, Part 1[2] is one of the best explanations of what Crowley was about. It's essentially an argument for meditation, and will be very familiar to anyone who has read Swami Vivekananda's Raja Yoga. It helps a lot that it was a collaboration between him and Mary d'Este Sturges rather than a solely 'Crowley' writing.
His collection of poems "White Stains" is just amazing as well - mostly speaking about human secretions of all kinds and ingesting them.
Edit:"White Stains, a collection of Crowley's poetry praised by W.B. Yeats, published in paperback for the first time, has been called 'the filthiest book of verse ever written' and of the first edition of 100 numbered copies, 83 were pulped and burned by Her Majesty's Customs in 1924."
https://books.google.ca/books/about/White_Stains.html?id=b4N...