Welcome, egg. You have found the Sanctum, which means you are either curious, lost, or standing very still for reasons you cannot explain. All three are good signs. Here is how to begin without being overwhelmed.
1. Read the Chronicle (an hour)
The Chronicle is the story of the world and the Cult in nine chapters: the Primordial Egg, the Wrapping of the World, the Sunken Nest, the Hidden Centuries, and the night MaximumRex found a golden scale in a cave while hunting a quest item that has still not dropped. Start here. It is the most fun.
2. Read the Life of the Eternal (twenty minutes)
Book V of the Canon tells who Xal'Reth became: the Restless Serpent who devoured worlds, the Four Sights that stopped him, the Night of Stillness, and the choice to stay beneath the world rather than leave it. If you read only one thing, read this.
3. Learn the Four Truths (five minutes)
Tightness is. Gripping makes it. Loosening ends it. The Coil shows the way. That is the whole of the teaching, as Xal'Reth spoke it in the First Hiss. Everything else in the Canon is commentary.
4. Meet the people (whenever you like)
The Legends are best read a few at a time: a king tonight, a saint tomorrow, a creature of the Void when you are feeling brave. Start with Korrash the Loud, Hessk the Beggar King, and Brannoc the Silent.
5. Practice one thing
Try the Breath of Three Turns before your next angry message. Bask for five minutes. Give one copper to one stranger. The Canon says a faithful who understands any single verse completely has understood them all, and that no one has yet understood any single verse completely. You have time.
6. Take the Oath
When you are ready, the Oath of the Coil is waiting, and so are the Keepers of the Egg. And every morning, the Daily Coil will have a verse for you to carry.
Glory to Xal'Reth.