In a world with shit reboots and bad soft reboots, it's kinda nice to see a sequel that treats its source material with respect. The basic plotline is the Jumanji board game changes itself into a video game after realizing that kids in 1996 don't play board games anymore. One kid gets trapped in Jumanji in 1996, and then the game is lost until 2017 when four more kids in detention join the game (similar to how the board game caught up the rest of the players in the original movie). The game sucks the players into the jungle, which is made explicitly clear is the same magical jungle that Robin Williams was trapped within for the first Jumanji.
The rest of the movie plays out as if it's a video game. Characters have popups telling them what they're good at or bad at (in the case of the Rock, he has no weaknesses; in the case of Kevin Hart, his weakness is cake which makes him explode), and everyone starts with three lives that get depleted as the game moves along. The "we're in a game" trope is used to justify some truly ridiculous stuff, all the teenagers-stuck-in-adult-bodies get valuable life lessons, and they even save the kid from 1996 who turns out to grow up into Colin Hanks.
I wasn't huge on the action in the movie. It was perfectly fine, of course, but shot with too much shaky cam as seems to be action norms these days. Even after George Miller reminded how action is supposed to be filmed in Fury Road, too many directors are making their cameras bounce around like a three year old on Christmas morning. However, I did enjoy the comedy turns - three really funny men were cast in the leads with The Rock, Kevin Hart, and the absolutely scene-stealing Jack Black, and I learned that Karen Gillan has decent comedic timing. The movie's gimmick was well-executed and heart-felt. It's silly and stuff, but you can't ask for more from a fun comedy film that has a nice message for the kids watching who are about to be teenagers.
And I will admit, it's hilarious watching Dwayne Johnson go from hamming it up while pretending to be a 16 year old insecure Jewish kid into the video game's dynamic and "smouldering" persona, then immediately switch back. Fantastic stuff.