This is the sequel to Heart Sick which I just finished up not that long ago. I didn't think Heart Sick particularly lived up to the hype I read in reviews. However, Sweetheart was a pretty good book! Putting the two books together made me like the first one better. I see how the first one was more of setting up the series. The second book contained a bit more action and made me more interested.
Sweetheart starts a couple months after Heart Sick ends. Susan is living with her mother. After being attacked by the serial killer in the first book, she understandably, doesn't feel like being alone. She's about to break the story of the senator's affair with a fourteen year old girl (this story line also started in Heart Sick) and more dead bodies are showing up in the woods. Archie Sheridan calls her to help with the new bodies. In the midst of all this, they receive a call that Gretchen Lowell, the serial killer and the woman that Archie has an intense relationship with, has escaped from prison. Archie's family, Susan and her mother as well as the various supporting characters go into lockdown while they look for Gretchen. That's as much as I'll say, because I don't want to spoil the story for people. :-)
I felt this book was much more fast paced than the first one. It was more interesting to me overall and the characters behaved more as I thought they should (ie: Archie's wife's response toward the end of Sweetheart; Archie's reaction to Gretchen this time, etc.). And again, I think the two books together are quite good. It appears from the ending of this one that the door is open for more in this series from Chelsea Cain. And I think people will hope she continues on after reading Sweetheart. 4 to 4.5 stars from me.