I have some questions
 

Firstly, (and not a question) I hope Dr. Genius dies a slow painful death.

Secondly, and maybe I'm stupid--it is a distinct possibility--but what actually WAS the joke?

Also, what is this Apology people keep talkin' to me about? I found no "apology."

Now I will be confused.

Ripped straight from the Wikipedia article (because it doesn't suck):

Spoiler Start:
One of the most twistedly entertaining parts of Nuklear Age is the ending. The first two-thirds of the novel set up the final third in a way that is difficult to forget. Clevinger refers to this as a "joke" because it is a "disruption of expectations", thus mirroring -- on a mechanical level -- the punchline of a joke. The "joke" is not meant to be funny, per se, but Clevinger claims that, too, as part of the joke.
:Spoiler End

Yes, thanks, but that doesn't actually tell me what the joke IS.

The joke is the whole book. It's not a "joke" in the sense that you're probably thinking.

It's just that a joke, like, "Why did the chicken cross the road? / To get to the other side," has a set up and a punchline. Nuklear Age has a set up (the tone of the first half of the book leads you to believe that nothing awful can happen) and a punchline (a great many awful things happen, and if you're paying attention, you can see that it was telegraphed as early as the first chapter).

As for The Apology, it was removed in the second edition due to reader feedback. It was meant to help clarify things, like why on Earth would you end a book that way, but it seemed to only further confuse people.

Okay, thanks, that makes sense.

Damn, that's brilliant.

Yes, I dare say, it is. And it just makes me want Atomik Age all the more.

Oh, indeed, indeed. (puts pipe in mouth)

Hm... The Superion and Crushtacean incidents seemed pretty awful to me... especially, in the case of the latter, for Angus...:end spoiler

It was awful in a cartoony way, so it's not really awful. What happens at the end for Angus was just about the worst way to die.

Really? People didn't like the apology? It finished the book of nicely, I thought. The book wouldn't feel right without it...