I bought a copy of 
Twenty One from a trip to Amsterdam as a souvenir.
The game: Twenty One by Steffen Benndorf and Reinhard Staupe, published by NSV in Germany and White Goblin in Netherlands in 2017.
Elevator pitch: Another quick die-rolling, coupon-filling game that keeps everybody active on everyone’s turn.
What’s in the box? A pad of scoring sheets, rules and six colourful six-sided dice. No pencils, this time, so provide your own. Everything is well-designed, looks nice and doesn’t take any more space than is necessary. It’s all very convenient and lovely.
What do you do in the game? The goal is to score points by filling your coupon with rolled numbers. You score from two sources: the raw sum of your rolls and the amount of exact hits you get. More is better.
The spaces on your sheet are colour coded, dictating which dice you can use to fill those spaces. Each space also has a number: that’s the maximum value you can enter there, and if you match it, you get an exact hit bonus.
The active player rolls all six dice and gets one reroll. If you reroll, you must reroll everything, except ones, which you’re not allowed to reroll.
Then everybody must use at least one number. You’re allowed to take as many as you wish, but only on the row you’re currently filling. You must take one, but if you can’t (eg. you’re only missing one number, and that die has a bigger number than you can take), you must cross out the leftmost open space on the row you’re on – and since the biggest numbers are on the left, that’s usually unpleasant.
Once you fill a row, you can then move on to the next row on the next roll, and whoever fills their fifth row first gets to end the game for everybody. Sum your scores, and the highest score wins.
Lucky or skillful? Very lucky. There’s some decision-making involved, mostly judgements on how many compromises should you make. I’m not sure you can play this particularly well – can’t really tell what’s a good move in this game – but you can definitely make bad moves.
Abstract or thematic? Abstract.
Solitaire or interactive? It’s a competitive solitaire. No interaction, but it’s a race, and how fast other players are filling up their coupons should affect how fast you’re moving, because if you lag behind, you’re going to lose.
Players: 2–6. The box has plenty of sheets, but there are only six different colour combinations in the pad, and it’s best if everybody has a different combination. Even though everybody is active on all turns, I’m pretty sure this is more fun with fewer players.
Who can play? Age recommendation is 8+, and I think it’s quite accurate. Certainly not higher, and smaller kids can play but not necessarily do well, unless they’re good with their numbers.
What’s to like: Well-designed, well-executed; plays fast, keeps everybody active all the time.
What’s not to like: It’s really quite lucky.
My verdict: Twenty One joins the line of Qwixx and Qwinto. All three are very good replacements for Yahtzee. Yahtzee is a fine game, but compared to these new, sleek games, the old classic is a boring downtime sessions, as you wait for other players to roll. All these new games keep everybody active on every round.
I like how Twenty One forces each player to act on each round; in Qwixx and Qwinto that’s always voluntary for the non-active players. Then again, those two games are probably slightly more strategic than Twenty One. All three are good die-rolling fillers, though, and I’d be happy to play any of them.
On the scale of Enthusiastic, Suggest, Indifferent or Avoid, Twenty One gets Suggest from me.
P.S. I’ve created an infinite scoring sheet for the game. It also counts the score automatically for you.