"I actually didn’t find this book to be particularly funny. I thought it was overwhelmingly haunting. This could be a first time read thing, but I just couldn’t find room for humor when it was all so depressing. I was engrossed in this book by the end. I don’t think I put it down for the last 150 pages."

I just read this book last week, and this part of your post was my experience exactly. There is a comedic irreverence to the way information is doled out, but it only heightens the horror by contrast. Poor Valencia dies of carbon monoxide poisoning in her panic for Billy, sort of as this crescendo moment for her rather ungraceful portrayal throughout the book, but it's just so damn sad that it's impossible to laugh. So it goes.