There is a real variety of Mahjong rule sets. Many countries have their own and some countries have many different sets. All rule sets are good and fun to play, but they do emphasize different parts of the game. The American game is about making fancy patterns, Japanese Riichi is a good for gambling and so on.
If you already know some people who play Mahjong, it's easiest to go by whatever rules they are using. The problems start if you need to start playing Mahjong from scratch. Choosing the right set of rules can be quite a challenge. Here's some help on choosing the rules and finding out proper resources to learn them. If you can read Finnish, you can skip everything here and head straight to Mahjong-opas.
Here are some helpful questions that may help you choose your rules. After the questions I'll list some resources to actually learn those rules.
- Do you want an easy game? Hong Kong Old Style rules are quite simple, they're low on special hands and tricky rules.
- Are you after a serious intellectual challenge? The Chinese Official Rules are a good choice.
- Do you like drama and gambling? Try playing Japanese Riichi. It's a good, wild game even if you don't play for money.
- Are you looking for a balanced, controlled game? The best options are Japanese Classical or World Series rules.
- Do you like building beautiful patterns? Accept no alternatives, choose American Mah Jongg.
- Are your friends anime and manga fans? You've got no choice than to play Riichi.
Hong Kong Old Style
This is one of the most popular styles of Mahjong. It was developed from Classical Chinese Mahjong before the WWII, mostly by making changes in the scoring. There's also New Style, which is also known as Shanghai style. The basic rules are the same, but New Style has a lot more scoring hands. The Old Style is restricted and simple and thus a good choice for new players. Once you learn the game and crave more complexity, you can add New Style hands to spice up the game.
Chinese Official Rules
Also known as Mahjong Competition Rules or Official International Rules (and abbreviated as CO, MCR or OIR). These rules are used in the Mahjong World Championship tournaments. These are as official as Mahjong rules come, designed by the Chinese authorities in 1998. These rules are written with bright ideals: the rules, for example, forbid swearing and smoking.
Also known as Modern Japanese, this ruleset was developed by gamblers and crooks in the 1950's. Since then it has become the most popular Mahjong game in Japan, surpassing the calmer Classical Japanese. It's a dramatic game, with large swings and some pretty strong luck elements, some of which may be removed if players want a more controlled game. Riichi is gaining popularity in West, too, as a part of the Japanese pop culture that become so hip in Europe and United States in last few years.
There are several ways to play Riichi, but the closest thing to official rules are the European Mahjong Association tournament rules. These are the best choice, particularly for a Western player. As far as I know there are no English-language books on Riichi.
This is one of the best forms of Mahjong for a new players. It's simple, easy and offers a balanced game, without major luck elements. Clever defensive play is important and making quick, low-scoring hands is a good strategy. Someone who likes a lot of drama and heavy swings will find these rules boring. The rules were set by a Japanese Mahjong association in the 1950's.
You can find English rules for Japanese Classical in the 4 Winds Mahjong Knowledge Base. If you're planning to play this variant, buying Eleanor Noss Whitney's A Mah Jong Handbook is a really good idea. The book has the rules and plenty of strategy.
World Series rules
World Series is a huge Mahjong tournament that is played annually. While the "official" world championships are based on the ideals of the Olympic games, World Series is closer to the World Series of Poker. In 2008, the winner was paid $500 000 and the total sum of prizes was million dollars. They're using different rules, developed by Mahjong expert Alan Kwan. Their rules are really good, too, balanced and well-designed. They are also easy to learn, while offering lots of opportunities for clever play.
You can find the rules in English on Mahjong Wiki.
American Mah Jongg
The way Mah Jongg is played in USA is a lot different, almost like a different game. The National Mah Jongg League published each year a new card with the hands that are allowed that year. To play the American Mah Jongg, you need to be a member of the league (or the competing American Mah Jongg Association).
To play Mahjong this way, you need to join National Mah Jongg League or American Mah Jongg Association to get the card (you can find old Mah Jongg cards in eBay). For rules, Tom Sloper's book The Red Dragon & The West Wind explains the rules well and covers the most common problems people have.