This review and others are posted at Read, Rinse, Repeat.
Note - This review contains spoilers of Zom-B, the first book in the series.
I give Darren Shan credit for trying something different in the zombie genre. Unfortunately, Zom-B Underground didn't work that well for me. B barely meets the definition of a zombie. Yes, she craves brains, but all of her mental abilities are intact. Where is the fun in that? It felt like a bit of a cheat, to be honest.
One of the focal points in the first novel is racism. B's father was a disgusting racist, and he passed down those beliefs to his daughter. Through much of the first story, it seemed to serve little purpose aside from making B's father as hateful as possible. At the end of Zom-B, B attempted to escape a zombie attack by tossing a black boy into a hungry zombie horde. Of course, her heart was torn out of her chest, so that didn't work out as intended. B's racist beliefs magically disappear in this novel, and it's made clear that the transformation comes about because B is (rightfully) now facing persecution as a zombie. I can buy that someone who has made a habit of dealing out prejudice may have a change of heart if that person found him- or herself on the receiving end. But we get back to main problem with this story, and that's that B, as a zombie, even has the capability to form these kinds of thoughts and rationalizations.
The violence and gore is graphic and relentless. I have no problems with that, but it become a bit numbing after a while when it seems that Shan relies more on the many ways to slurp a brain out of a skull than he does on interesting storytelling. There are some hints that B may begin to lose her mental acuity in the future novels. I don't know how that will work if the books continue to be told from B's viewpoint, but I think that's what needs to happen if this story is going to become interesting again.