[wwweston]

I like Dominion, it's got some of the same mechanics and is a an easier game to set up and explain.

But it's missing one key thing that Puerto Rico has -- the depth of subtle interaction. Yes, there's some interaction cards in Dominion, but with PR there's this level of play that goes beyond blocking other players and into providing incentives for them to do things with a timing that's advantageous for you (and slightly less advantageous for them, but not so much that they can resist :).

Not a whole lot of games like that.

[VLM]

If you want a highly interactive card game, maybe pathfinder card game? Be sure to go on line and print out the errata which is several times longer than the rules as shipped, although its certainly good fun even without corrections,or optimizations. Note its co-op which tends to be pretty binary, people seem to either love co-op or hate it.