I don't know if it is the author's writing style not being suitable to where he has taken the story or he is just taking shortcuts and rushing, but this book is a letdown from the previous two. I suspect it is a mixture of both. The writing style of these stories was perfect when it was one man trying to survive a momentous disaster, but it doesn't translate well into the increased action of the post apocalypse societies. The author is able to get the feeling of monotony across to the reader in an interesting way and he is decent at building tension, but he can't handle action scenes well. There are also segments that feel a bit rushed, but those tend to be the action scenes and so it might be his writing style.
Also, the bulldozer zombies are annoying. When the horde passes through an area and the author uses landscape descriptions that seem significantly worse than the aftermath of a major flood or violent tsunami it gets annoying quickly. How exactly do zombies knock down all the buildings and trample all the structures in a wide swath of land? This is just one of this author's "magic zombie" features. Most zombie fiction relies on stupidity of the characters and magical acts of the zombies to make zombies threatening and this is just one of the ones used in this series, but it is annoying and pulls me out of the story in a major way.
Still, it isn't a bad book. I won't be continuing the series, but I can see why someone would. I would definitely recommend this series to anyone that was a fan of zombies.