Joseph Heller, Something Happened, how did you read the ending?

I’m trying to make sense of this book. The ending was very strange to me. It seems the most common interpretation is that Bob is actually progressively slipping into insanity as the book unfolds, and hasn’t been able to confront that his little boy actually was hurt in an accident, and then smothered by himself.

Originally I didn’t read it this was. In an interview, Joseph Heller says that he intentionally wrote the book such that no one cause suffices to explain Bob’s state. Of course, he could be talking about the more general unhappiness Bob experiences. With this in mind though, I originally thought the car crash and smothering was Bob having essentially a day dream of something he is afraid of having happen. For it to be factual felt out of nowhere. But then the final chapter being so positive seems to strongly support that, yes, Bob is insane. He doesn’t tell his wife he loves her, he doesn’t buy his daughter a car, they don’t keep Darek, etc—it’s just a fantasy.

I’m curious how others read this and what they thought, and if it’s changed at all.