You play as Luigi, trying to save your friends in a haunted hotel that has taken them hostage. You have a trusty vacuum that you can suck up ghosts with, but you can also suck up coins, gems, and other items. You can also shoot a plunger at certain items and pull them off with your vacuum. Additionally, you can hunt for secret areas and clues with a flashlight. However, the best part of the game is Gooigi, your trusty sidekick who you can produce at anytime, who can squeeze into sewers and vents and reach places Luigi cannot. You can use Luigi and Googi together to take down enemies, and there are a lot of clever puzzles throughout the game. There are 15 floors, each taking between 30 minutes and 2 hours to complete, depending on completionist you want to be (the gems are genuinely difficult to find). You seem to quickly possess almost unlimited amounts of money that you never really need, but it's still fun to see coins flying into Luigi's vacuum.
Some cons to the game include that the game is very repetitive, after a while you're doing the same thing over and over (this is a 20 hour game, which feels too long for a Luigi's Mansion game). There are also too many bosses, many of which felt cheap in their gameplay. There is a boss on every level, totaling 15 bosses plus the final boss, which didn't feel necessary. There are also mini-bosses on almost every level, adding even more to the boss fights. Sometimes, immediately after beating a boss and being able to move onto the next level, a cat will steal the key and you have to chase it around the hotel multiple times, which is a huge pain in the ass and nothing about it is fun or enjoyable. Lastly, there is no way to fast travel from one area that you've visited to another, so you have to physically go find the elevator on the level and travel around that way.
The highlights include the puzzles involving both Luigi and Gooigi and trying to find the elusive gems. The Ghostbuster's theme is entertaining throughout, and Luigi's constant state of fear is really amusing to watch. There is also a storage facility where you can look at all the ghosts you've caught and gems you've captures. Every floor has a different theme, and the gems and boss would match the theme. Some themes were definitely better than others, but generally there was a great variety (a movie theater level, a pirate ship level, a gym, etc.). It was consistently enjoyable to see what area Luigi would wind up in next.
Super cute graphics, the animations were adorable. Gooigi was especially adorbs, and Luigi's dog friend. The artwork for all the different ghosts, especially the boss ghosts, was extremely well done. Overall, some of the best graphics on the Switch are offered here.
There is no real variety in the music; it mostly plays the same music throughout the entire adventure. That one song is fine, but it would've been nice if there was more variety.