Jenga is 54 hardwood blocks, a stacking sleeve that keeps the tower straight while you build it, and the rules. It does not need much more than that.
The rule fits in one sentence: on your turn, pull a block out of the tower and put it back on top. Every turn leaves the stack a little less steady, until someone brings it down and the round is over. Then you simply build it up again.
A game lasts a few minutes; an evening lasts as many games as you feel like. You can play it alone against your own record, or with a table full of people, and it works as well at the kitchen table as in a holiday cottage. Hasbro states the game is from 6 years.
One of the few games where grandchildren, parents and grandparents sit down together without anyone having to explain anything first. That is part of why it stays such a reliable gift.