Linger

I adored Shiver, the poignancy of Grace and Sam, and the overall mood of the book.

While Linger didn't grab me as hard, I still enjoyed it.

Delving deeper into the Cole and Isabel characters was interesting, but the frequent POV changes tore me out of the story.

The relationship between Sam and Grace is beautiful and looking forward to Forever.

I enjoyed the plot of this one more than the first, and with the additional POV's from Cole and Isabel we get a break from the floof of Grace and Sam's relationship.
While Cole, a brand-new character, seems to have developed and grown impossibly from one moment to the next, Grace and Sam seem very stagnant - Grace seems to have even reverted a bit to, albeit a more realistic (see: immature and naive) version of a 17 year old, a really annoying and selfish teenager. She seemed very independent and self-aware in the first book but as she's become more reliant on Sam, she's seemed to lost a bit of herself and now she's exactly what her mother thinks she is. When her parents find a boy (though in pajamas) in her room in the middle of the night and call her out on it, Grace completely rebels instead of self-reflects (as you'd expect from a 17 year old and also proving her mother's worries completely legitimate) and acts like a spoiled child. Sam is supposed to be 18/19 in this and been through a lot of hell in life but, while not acting like Grace in that way, still does not act like an adult.
Besides all that, the actual plot is very interesting with Grace starting to feel the effects of “the change” to the point where it's physically killing her along with Cole's whole character arc. It's also been riveting to see how Isabel is changing and developing as a character, now that we can see her side of the story. There are a few holes that I would like to be addressed, the biggest one being how Cole suddenly changed from a complete devil-may-care asshole to suddenly selfless and caring after his one (self-labeled) “good deed” of not sleeping with Isabel. It seemed very sudden.
Overall, a good sequel, maybe even better than the debut. I'm excited to get through this series to see what kind of conclusion the author devises.