Luigi's Mansion 3 is exactly what you would expect if you have played the other 2 in the series. You play as Luigi primarily and an alternate form you unlock later in the game. You'll have to use both forms to finish the game, find hidden gems, solve puzzles, and defeat all the ghosts! You are the Ghostbuster of the Mario Universe.
You take on the roll of a Ghostbuster with your handy dandy vacuum. You'll have to save all your friends from some ghosts. You'll have multiple puzzles to solve, some easy and some difficult. There have been a few we gave up on. We just couldn't figure it out and looking it up just feels like cheating.
The bosses are pretty fun. One fight in particular is my favorite, it's pretty indepth and without giving spoilers there are multiple phases you have to execute in order. It's pretty obvious what you have to do so it doesn't feel cheap if you lose.
The co-op doesn't unlock right away which is a bummer. It's maybe 30 minutes to an hour into the game to unlock it. Each character can do different things. For instance Luigi can touch water while Gooigi can walk through bars.
I've had a blast playing this with my girlfriend. She isn't a gamer by any means, but she tries her best and some of the games she likes (Lego and Sims) overlaps with what I enjoy as well. Luigi's Mansion was a good mix for us. It wasn't overly complicated for her, and it was challenging for me.
Overall I love the game. It is the perfect challenge mix for me and the girlfriend, and it's always nice to get some couch co-op going. The puzzles are fun, and the bosses are great. I can't recommend the game enough.