Did you finish it? I just reached Chapter 3. It's impressive how many things there are to see and find in this game. I thought I had probably found just about everything in the first two chapters, but a quick glance at a walkthough showed I missed quite a bit of stuff.
Do you mean chapter 3 or act 3? I think there are 3 acts, 11 chapters. I'm almost finished, in chapter 9.
There are a lot of things to discover, photos to take, the geocaches, the silly bears and toys, the things to repair... most of which is optional.
And have you noticed those codes laying around? People are still trying to discover their meaning. I admit it's entirely meta and a little OCD, this one should give you an idea how crazy this is. I'm definitely not going down that path.