This game is a progression of text based games, but adds pictures to the style as well as using a menu system to make moves instead of a text parser. You take action and move using the menu system. You also have a notepad that allows you to see your inventory and learned spells during the game. While the game encourages you to explore your surroundings, you must be very cautious which moves you make, because in many cases a single wrong move ends in the death of your character.
The story starts rather dramatically. You swerve to avoid hitting someone in the road and wreck your vehicle. You come to in the vehicle, with your passenger missing. After leaving the car (which you can die in depending on your actions), you discover a large mansion, where you begin the search for your sister (in other versions it wasn't always your sister you are searching for). Without spoiling the story too much, your search takes you beyond the mansion to other buildings on the grounds, and you will have to deal with everything from ghosts to zombies, demons, even giant spiders. You have to be very careful what actions you take in order to get past or defeat these obstacles, as almost all of them can slay your character if you make just a single wrong move.
With all that said, whatever you do, please don't use a walkthrough to play this game. Uninvited is best experienced by just jumping in and learning from trial and error. Besides, one of its best features is the horrid ways your character can meet an untimely end. Some of these endings are pretty brutal for an NES title, and some of the text descriptions in other versions are even more brutal.
This game, along with the entire Macventure lineup, was both a basic evolution of text based games and a forerunner in the point and click adventure series, made famous by later titles on the PC like Myst and The 7th Guest. In my opinion though, those games pale in comparison to the games released by the MacVenture team. Their games have a flow that I feel later point and click games lack.