Tobaku Datenroku Kaiji continues Kaiji's struggles and is the arc directly after where the anime leaves off. If you had watched the second season of the anime, you might even recognize that the ending theme was an animation of some of this arc's early scenes where Kaiji is forced into cohabitation with Mikoko.
Quickly, the story thrusts Kaiji into a situation where he gambles for more than he's worth, a mainstay of the series at this point.
The characters in this part, both old and introduced, are compelling. Kaiji's opponent is absolutely ominous and helps makes this my favorite part in terms of characters. Coming from the second arc of the series where he fights The Bog, I felt that the combination of characters, situation, and game played are all better and more exciting -- if you understand riichi mahjong, it's even better.
I've thought quite a bit about whether you need to understand mahjong to enjoy this arc. And really, while you don't need to, it would of course enhance the experience. I myself had been playing mahjong for more than a year by the time I read this arc and the logic used in the game is not anything bizarre that a normal player wouldn't learn if they played for more than a week or two. Some of the terminology may be lost on someone unfamiliar, but even then it doesn't often matter. There is just one scene in particular that I wonder what someone unfamiliar would think, because without working knowledge of the game the scene loses some tension and panic. Overall, it should not impact the reader too much.
It also helps that it is the trend that the games played in the Kaiji series are modified, usually simplified, versions of real games. Or, original ideas where the rules can be deep but understanding the game at face value is simple. This is to say, I think the way the game is explained suffices. A lot of the complexity of mahjong is eliminated, and the type of game it is is summed up perfectly very early on when they reveal the name and rules.
If you have enjoyed the previous Kaiji parts or want more of what the anime offered, don't be intimidated by mahjong. The reward is what I believe to be the best arc.
