The Fear Institute question

There are references to the first 2 books and spoilers about the first 2 books so if you want to read the whole series start at the first book.

You should read the first two because they're excellent. I don't think it's necessary, though.

My brother and I read the books together, and I think you should read them in order. He read the second one first, and then the first one, and I constantly had to fill in plot holes. I don't think you need to read the others first to understand what's happening in Book 3, but if you want to understand some of the more subtle plot points, or especially the importance of certain acts and character development arcs, then you should definitely read them in order.