A complex game, and one of the best strategy board games, the designers, Inka and Markus Brand are from Germany and have designed over 20 games. And it shows in the masterful game that is Rajas of the Ganges. A brilliant game, there is a time investment to learn the mechanics, though the upside is a board game you can play repeatedly.
This is a worker placement + dice rolling game, and the essence of play is as follows:
1. Choose where to place your worker on the board, if and only if this works with your goals and the current rolls of your dice
2. Gain money, dice, points, karma, etc
3. Continue to place workers, one at a time, until all players run out of workers
4. Win when the two tracks on the board - the money (wealth) track and the fame points track meet or cross one another. The tracks are going in opposite directions around the board.
Of course, there are a few other intricacies such that in order to place a worker, you usually pay in money or dice, though not always, and there is a province board for each player where you can place province tiles and be awarded bonuses.
However, much of the mechanic is mentioned in the steps above. The bigger and more important part of the game is that there are many areas where a player can choose to place their workers. Thus, gaming the action options, and acquiring your points and wealth faster than other players is where the fun and skill begins.
For example, do you give up dice in order to build a province tile which can provide points (though you have to also give up something to cash those in) or do you move up the river and give up money for dice, karma, or points, etc, depending on where you land? And in which order do you go, as once you place a worker on an action space, another worker of yours or any other players cannot be placed there again until the round is over and a new one begins.
Because there are many choices players can make, as well as strategies to implement, for instance, a player could choose to get lots of fame points and fewer wealth, or vice versa, (and plan which mechanisms to use to execute their strategy), my guess is that the game remains interesting over several times playing, especially as you wrestle with what other players are doing. Certainly, there are enough action choices to really use the board and execute an ingenious and original win, and still try a different method next time. This is really part of what makes the game brilliant. Really, all you have to do is LOOK at the Rajas of the Ganges board, and you'll realize what a full and remarkable game the powerhouse designers created for us to play.
And, the kicker, I just love the fact that players can accumulate 'karma' which allows them to turn any die to the opposite side, e.g. if you rolled a 1 you can use 1 karma to flip it to you a 6.
Just another demonstration of how smart the game is - and a reminder to be a good person, so you have good karma!
For a really comprehensive review, here's a good one.
For a full set of rules, see the pdf here.