As Euchale said, it is another GTA game, all of them have the same concept, and if you liked all other GTA games (except for perhaps 4 which was a nasty port); you will like this one.
Singleplayer is like it always has been, fun story to play through and classic GTA ending with a twist. I liked playing the singleplayer again, after the launch of the ps3 version.
Online is a clusterduck, I don’t play in open lobbies myself; I mostly play with friends doing missions and stuff. I did a heist with a friend today, they unlock at rank 12 (heists, not friends) and adds a whole new fun to the game. I guess you could say it’s a mix between GTA and Payday, plan the heists, get the equipment and crew, and then perform the heists. The experience didn’t seem to be insane, at least from the tutorial which is the one I did. But the money rewarded were nice.
Do I recommend it? If you haven’t played the singleplayer before, I definitely recommend it. If you have played the story and don’t care for online, I wouldn’t suggest buying it. And if anyone need someone to play with, I'm usually open. Especially when the other europeans have gone to bed.
get it on Xbox One or else.