The Remaining series does not fall into the reference category or even non fiction. It is a survival novel (or set of novels) that is based in the zombie genre.
The Remaining is different for most readers from a great many zombie books however. They are, in most cases, accurate in its weaponry, tactics and strategies. If you have ever served in the military, a lot of familiar techniques and procedures will be on display. If not, it is a fun series that can actually raise your heart rate.
Not all books have to be reference or educational. These books are simply entertaining. Enjoy!