The only thing that stands between the people of New York and the rabid people (zombies) of New York are the earnest and dedicated soldiers of the US army who have been recalled from Iraq and Afghanistan. We witness the action as it becomes clear that the plague is beyond the control of government and its military. The book covers a few short, harrowing days as the city is lost to the infected. The original military mission to maintain order proves futile and soon becomes one of simple survival. The pace is great, military jargon and operations largely accurate, and the "zombies" interesting as they can be killed without the usual headshot. The part of the story revolving around a potential cure in a local research facility was not required but did not take away from the overall thrill ride.
As the cause of the "zombie" outbreak is discussed very early on, it's no spoiler to say that it's caused by a rabies-like virus that makes people attack/bite other people. The good news is that means the infected aren't "undead", you can kill them any way you like. The bad news is that there's a whole lot of people in New York, and very soon a smallish-infection turns very serious.
The book follows the actions of a US Army company tasked with guarding a hospital. I found it ironic that a Canadian author was writing about a US Army unit (especially with all the patriotic talk in the book), but the author does a good job of conveying a sense of a true military unit. The "leading" character is a lieutenant in that company, but there are lots of other interesting characters who are involved. In that regard, this book is short enough that the flaws in the characters aren't exposed, but long enough that they aren't just names on red shirts. You can care a little about them.
As for the action in this book, it's pretty intense. As it follows the outbreak, it naturally starts off slow and builds up to a climax at the end of the book. The action at the small scale seems very believable, with some people refusing to fire, others panicking, others staying calm, etc. At the larger scale, the Army as a whole was pretty stupid (poor use of helicopters, especially final scene, no bait & switch tactics at the higher levels, a single tank, bulldozer, or steam roller! could have won most of the city). But as the book is short and highly focused, you can largely forgive those oversights.
Thus, this certainly isn't the best action story I've read, nor the best horror story. But it is a good book. I think the author made a great choice when he kept this book relatively short and to the point. That kept the action intense, kept the reader from wondering about too many plot holes, and made the story seem more realistic overall. The settings were vivid yet familiar, which added to that. If you're a fan of the genre, I'm confident that this is a pretty safe recommendation for you.