First story is creepy, second is interesting...
I'm not really sure how the first story fits into this book... or maybe the book is supposed to be centered around the first and the second short story doesn't really fit. Either way, there are two very very different stories in this collection.
The first one is a creepy story about a guy who talks to himself and/or hears voices in his head... he has moments when he blacks out and when he wakes up he finds out about the things that happened while he was "out." Seemingly, the guy (when "himself") is a man with some sort of disability that leaves him with the mind and motives of a child. However, he can somehow control events with his thoughts, without realizing it. The second "person" in his head is emotionally older - at first he seems to want to protect the other self by guiding him (and cleaning up after his messes) but toward the end you realize that maybe this second self isn't any better than the first... the only difference is that the second personality KNOWS what his actions do, while the first, mentally handicapped personality isn't aware of the impact of his actions when he's causing them to happen.
Overall, creepy story. Good, but didn't fit the Apocalype theme I got from the title of the book.
The second short story is more straight-forward. Set in the recent future, a plague was let loose by aliens that transforms humans into these alien, or sometimes into enhanced versions of themselves - people who can be used as a weapon to kill the other, transformed humans. People falls into different categories: hosts (basically the boss level), husks (humans who have been trained of thought/emotion/soul by the hosts) who now act as zombie-type soldiers - they are clearly controlled by the hosts, and then you have the humans who were transformed into animal-type creatures - also can be controlled by the hosts, by dangerous in and of themselves because of their claws and size. The story is set in the middle of a battle, where one of the first "warriors" (aka enhanced humans who fight against the monsters) is fighting alongside a younger woman. You get snippets of the story of how the plague started... and how it could have been stopped... through the thoughts of the man. This short story goes along with a longer version of the Nanite-plague/invasion called "Children of the Plague" by Gregory Carrico. I highly suggest that if you like this short story (or if it interests you) that you read the longer book to see more of the world.