As you may already know, the National Mah Jongg League has been publishing updated rules & winning hands on a yearly basis since 1937! In addition, they answer members' questions in newsletters, so it's hard to keep track of ALL of the rules. But it is possible!
Start with the current year card. You can purchase this on the National Mah Jongg League website, or on their Amazon page here: https://amzn.to/4ftTY6y. This is the official account, be careful ordering from other links as most are counterfeit!
If you really want to deep dive into the rules, I also recommend "Mah Jongg Made Easy" which was updated by the National Mah Jongg League in 2024.
On top of that, Michelle Frizzell, the founder of Mahj Life, has created a document with this additional rules you can find here: https://cdn.shopify.com/s/files/1/0675/6197/9975/files/Rules-not-in-Mah-Jongg-Made-Easy-2024-Insert-20240922.pdf?v=1784854628
