Having played "normal" dominoes a few times, and got bored of it fairly quickly, we decided to try Tri-ominoes. It's absolutely brilliant! Very easy to pick up, and rather addictive, we have found! In fact, we are so competitive that we have set up a league table!
The instructions/rules are easy to follow - also there are instructions for simplifying the scoring if children are playing. This game is very good for practising mental arithmetic.
So far I have only played this game with 2 players - I imagine it will be just as good (if not better) with more players. Highly recommended. In fact, it's so good that I have bought a second set to keep at our caravan!