I still get a little thrill thinking about the first time I opened something by Aleister Crowley and realized he really meant magick with a 'k' — a whole vocabulary and practice that’s not stagecraft but occult work. If you’re diving in, start with the essentials: 'Liber AL vel Legis' (usually just called 'The Book of the Law') is his spiritual manifesto and the foundation of Thelema. For practical ritual work, the big, infamous text is 'Magick in Theory and Practice' (often printed within 'Magick (Book 4)' or referenced as part of 'Liber ABA') — dense and blunt, full of ceremonial structure and Crowley’s takes on will and ritual. For a gentler, more conversational doorway, I’d recommend 'Magick Without Tears' — it’s a series of letters Crowley wrote that feel like a tutor explaining complicated ideas in plain language.
If your curiosity runs to systems and reference works, '777 and Other Qabalistic Writings' is an indispensable compendium of correspondences (great for Tarot, ritual, or symbolism work), and 'The Book of Thoth' is Crowley’s magnum opus on Tarot theory and the Thoth deck. Visionary and Enochian experiences are best explored in 'The Vision and the Voice' (with its travel through the Enochian aethyrs). For ritual grimoires and spirit work, his edition and commentary on 'The Goetia' collects material on the Lesser Key of Solomon with Crowley’s practical notes.
Crowley’s writings span polemic, poetry, ritual manuals, and mystical journal entries — so the tone shifts a lot. If you want a reading path: read 'Liber AL vel Legis' first to know the creed; then 'Magick Without Tears' for clarity; follow with 'Magick in Theory and Practice' when you feel ready for heavier ritual work; supplement with '777' and 'The Book of Thoth' for correspondences and symbolism. I keep revisiting these and every read gives me a new lens.