Throughout the books, readers are able to see as Grace and Sam spend their limited amount of time together, searching for a cure to keep Sam from turning back into a wolf. Without spoiling anything for you in case you haven't read it, they find a cure for becoming a wolf and try it out on Sam and another wolf, it works on one person but not on the other.
I am currently reading Linger, the sequel, but it is taking me much longer to read it then it did for me to read the original. I truly enjoyed Shiver, I thought that it was extremely interesting although not entirely believable. It is nowhere near on the same level as Harry Potter, Hunger Games, Twilight, Divergent or any of the many other series that I have devoured in the past- but it definitely entertained me enough to want to continue reading!
Hopefully I will be finishing Linger soon and will be sharing my review on that as well!