+1 to what DBond has said.

I usually wait until I buy "games" as I'm a flightsim guy, but this purchase is easily the best purchase I have ever made regarding a game on PC. I've been playing it since it's release at least an hour or two a night and I'm only 26% done with the game. I played last night, completing 3 missions and I went from 24% to 26%. The game is absolutely massive. There is so much to do and experience. I just started Chapter 3 and there are 6 Chapters in it as well as 2 prologue chapters apparently. What I love about the game is that you don't have blow right through the story. Chapter 1 is basically linear and will lead you into the story. Once you get to Chapter 2 the world opens up. I'm still nowhere close to seeing the entire map yet because of all the side things I do just for fun.

It's a pretty incredible experience.