** spoiler alert ** 
 I really did love Linger, although I feel that it just wasn't as good as Shiver. However, the ending was really amazing, and they might actually be on the right track to solve the shifting-from-human-to wolf problem. 
 In the story, Sam is now a human for good after being "cured". But still, they have to deal with the problems brought about by the wolves. The new wolves that Beck created are out, and are causing problems with the constant worry of changing in front of people that don't know the secret about the wolves. And Grace is showing signs of a sick wolf that is close to death, even though she never changed into a wolf. 
 I really liked the introduction of the new characters, and the delving into the old ones. We learn more about Isabel, and how she feels about her brother Jack's death and her guilt about it. And we meet Cole, one of Beck's new wolves, who before being bitten by Beck, was the lead singer of a well known rock band. When he was a human, he cheated on his girlfriend, did drugs, and tried to escape the reality that he was a genius like his father. he is also the main reason that Grace doesn't die, because he realizes that the death of the wolves (and, eventually Grace) is due to the wolves not being able to shift. He also figures out that the wolves don't shift because the temperature changes, it's due to a certain part of the brain, and its reactions to things. 
 I can't wait to read about what Sam will try and do to come with a cure to save Grace, himself, and the other wolves in the next book!