Review: "Shiver" by Maggie Stiefvater

It's time for a new post, right? And I haven't done a review for a very long time.

Shiver by Maggie Stiefvater

I can't help it. For some strange reason I can't stay away from paranormal romances. Shiver, for all intents and purposes, is right up that alley. I can't remember where I first came across it. I do know that I plopped it onto my to-read list (on a digital sticky note on my computer), and when I got a couple free audio-books, I downloaded it.
The skinny on Shiver. It takes place in a small town in Minnesota. It is told from the point of view of Grace and Sam, alternating in first person. Grace is saved from a wolf attack at age eight by an unknown wolf. As she grows older, so does her passion for the wolves that live in the wolves outside her home. Then she finds out that they're actually werewolves.
The good things first, which is how I always like to start my reviews:
* You'd think that alternating first person POVs between Grace and Sam might give you something like mental whiplash. The good news is that Stiefvater does it very well. The two narratives flow quite seamlessly together.
*The characters are pretty believable and likable.
And, I have to be honest, that's where my praise ends. At best, Shiver is a tribute to Twilight, at worst it's a barely concealed copy. Granted, much more likable, strong, less whiny and needy Grace replaces Bella. Edward is a werewolf named Sam. The dramatic, teen, true-love story is basically the same.
One large plot hole pops up right at the beginning. We learn that the cold weather changes the wolves from their human form to their wolf form. What's the first question that pops into your mind? It's probably the same one I had when I found out this is why the wolves changed. Why don't they move to Mexico? Stiefvater does finally take care of this question late in the book. And the explanation is plausible and creative (the warmer temperatures cause their bodies to be more susceptible to even the smallest changes in weather, making it easier for them to change into wolf form at the smallest drop). The problem is that this explanation comes far, far too late, especially since the question presses on the reader's brain from near the beginning of the book.
Another question never answered? Grace is bitten by the wolves at age eight but never changes, and the explanation that Grace and Sam discover just in the nick of time is a good twist to the story. The problem is that Grace's wolf rival Shelby attacks Grace near the middle of the book and bites her again. Stiefvater never explains why Grace doesn't change after this bite, or even adresses it.
In short, I'm intrigued enough by Shiver to want to know what happens in the latter two books, but not intrigued enough to actually read them. I'm currently searching for a detailed outline. ;)

I'd love to have a discussion with any of you who've read it? What's your opinion? Have I been to harsh? Do you agree?