Which books am I missing?

Just bought this set(second hand). I read the first 3 and absolutely love them. I looked online and there's a couple of different versions, extras, subsequent, etc. I'm just wanting to make sure I have all the books in the right order.

Just bought this set(second hand). I read the first 3 and absolutely love them. I looked online and there's a couple of different versions, extras, subsequent, etc. I'm just wanting to make sure I have all the books in the right order.