The ending sentence of the book...do you think Piranesi/M.R.S. had reentered his "Home" again permanently or traveled into another world? Or is that just a sentimental line? I thought I remembered reading that the Home had a tendency to shift or gain additions, so maybe he couldn't handle the real world and craved the Home too much (like Ritter), which could have been altered based on his new interpretation of life.