Boomerang could be described as a card draft game (like 7 Wonders or Sushi Go!) mixed with a Roll and Write game (like Yahtzee or Qwixx for example).
In each round, players choose one card from their playing hand, then pass the rest of their cards to the next player. Are you going to take what you really want, or a different card to deprive another player of something cool?
At the end of each round, players mark different things on their score sheet, corresponding to what they've won with the cards they've selected. Players earn points for seeing curiosities, seeing animals, and so on. After five rounds, the player with the most points wins.