Chuck Wendig channeled his inner Stephen King for this one. It was so gripping it kept up me up late for 3 nights. He was also not afraid to pull in some of the elements from modern politics in America. If you knew nothing about what has been going on you might think these side references were over-the-top flights of fancy. Maybe in 20 years people will think that again, but for now it highlights just bizarre things have become.
What made this book differ from his other works, aside from length--this comes in about 800 pages--is the story line, which is more plausible than the Bad Blood series story line (those are great reads too if you're into sardonic vampires who accidentally end up as last chance for humanity in a world of zombies). In this one a zoonotic disease (a disease that can jump from animal/insect host to human) begins to infect and kill people. As you read there are many questions, like, can the CDC find a cure before it's too late? How does this disease relate to the sleepwalkers? What is the AI's part in all this?
The characters and their background rounds out the book too. It's not just the CDC people trying to find a cure, but the backstory of a main character, the political fall-out from past decisions, the loggerheads with other agencies and head of the CDC itself all play a part in making the character feel like someone you have known--it brings him to life. Similar writings and backstories bring other characters to life as well.
One of the reasons the book was hard to put down was because you became so invested in these characters as if you knew them. In some cases I found my heart pounding when they were in danger or some confrontation, even when it was just a two people trying to impose their agenda on the other person without any violence---sure, I'll just put the book down and go to sleep while my pulse rate has jumped to a 100 bpm.
Another good bit of writing in the book is where he shows you a scenario that sounds horrible, but the scenario is necessary to avoid something even more horrible, or because there was no real practical choice--the characters agonize over decisions made, wrestle with moral consequences over what they should or should not have done, while you, the reader, are trying to figure out what you would have done differently, or if anything you did would make a difference at all.
So, great book, pulls you in, and there's lots of book there to be pulled in by.