I loved this book! I have not seen the movie before so I was constantly reassessing through the book what I thought was reality. It kept me guessing up until the end which I thought was clever. I did not expect the plot twist.
I had a different interpretation. I think his wife did kill their children and he killed her, and it was those events that contributed to his insanity. I think what happened to him long-term is that he gets the lobotomy. What we don't know is what was reality for him at the end. Did he truly regress like he had in the past? Or did the elaborate plot by the doctors to make him lucid work and he pretends it didn't because he can't live with the reality that his children are dead and he murdered his wife and he'd rather be lobotomized to be unaware? Quite a shocking and brilliant ending, I thought.