If you haven't played any Disgaea before, then it's likely to be a massive departure from any game you know. The developer do release a bunch of other games with somewhat similar gameplay, but those are all rather lesser-known and I'd assume you haven't tried those before. Superficially it may seem the same as a Fire Emblem or Final Fantasy Tactics, but the core of the game is very, very different. I just want to make sure you're prepared for what you're getting into.
First of all, the game script is trying for funny. The humour may or may not land for you, but that's the type of story they're telling. Second of all, the narrative in this series is... not entirely the main attraction. I always have fun playing the story part of these games, but the bulk of the content is not narrative, and only opens up once you clear the story. The focus here is on powering up your characters to a ludicrous degree. During the story, in addition to main maps, there will also be procedurally-generated dungeons available to you. These dungeons will help you improve your characters, and your gear. Once the story is over, you have the option to continue pursuing these procgen dungeons at an ever higher level. The better the gear you have, the higher the level of the enemies you'll face. Sort of.
In addition to these dungeons, and as a sort of an end goal for doing them, you will also have access to a number of optional boss battles. To clear these will require characters and gear far better than is required to beat the story. You will need to spend a lot of time powering up in order to face these challenges. Fortunately, the game offers many intricate and complex systems designed to help you power up faster and more efficiently. To some extent, at this stage of the game, it's an optimisation puzzle as much as it is anything else.
If any of this sounds interesting to you, then maybe you want to play Disgaea. If it sounds off-putting, then I wouldn't want to suggest that you should not play, but you might not find that you get full value for money out of it.
If you have specific questions, please ask. I could talk about Disgaea for hours, and I'm sure that plenty of other members could as well.