I Don't Want to Kill You

The final book in the "John Cleaver" trilogy by Dan Wells, following I Am Not a Serial Killer and Mr. Monster.

John Wayne Cleaver is still not a serial killer, because to be a serial killer you have to kill people. Of course, his first action after successfully defeating Agent Forman was to use his cell phone to contact one of his associates and announce that he plans to kill her - even though he has no idea what she might be able to do to him, or force him to do to his family...

What's more, he wasn't expecting Nobody to come with backup.

Tropes used in I Don't Want to Kill You include:

Betty and Veronica - Brooke and Marci.
Bound and Gagged - John has a brief moment of imagining Marci this way.
Chekhov's Gun - The Handyman arrives at the same time as a chain of apparent suicides.
Demonic Possession - John and Father Erikson discuss this as a possibility, although it's only partly accurate.
Driven to Suicide - Nobody's victims. Nobody herself, for that matter, recurringly.
Even Bad Men Love Their Mamas - Assuming that we can qualify John as bad, this trope applies. Although he doesn't actually realize it until after she dies.
First Girl Wins - Because the other one died.
Heroic Sacrifice - Mrs. Cleaver
Like You Would Really Do It - Invoked by Nobody. John wouldn't really kill Brooke's body simply in order to kill Nobody, too would he? Yes, actually, he would.
Mama Bear - Mrs. Cleaver.
Police Are Useless - Averted. John gets quite a lot of information out of Marci's father. Agent Ostler turns out to be trying to hunt down Nobody, too; and if John had known she was trustworthy quite a bit of death could have been averted.
Red Herring - For the characters as well as the readers. When the Handyman arrives in Clayton John assumes he must be the demon and spends most of the book trying to profile him based on that assumption. Similarly, the revelation that the Handyman mutilated the eyes of his most recent victim right after John had a discussion about another serial killer with a fixation on eyes with Marci and her dad.
Reluctant Psycho - John will get worse before he gets better...
Sacrificial Lion - Marci, and Mrs. Cleaver.
Sociopathic Hero - John Wayne Cleaver. Averted by the end, as in grieving the death of his mother he realizes he does have the capacity to love after all.
Stalker with a Crush - John hasn't entirely gotten over this tendency. It also turns out to be Nobody's entire modus operandi.
Taking You with Me - Done by Mrs. Cleaver, to Nobody.
Talking to the Dead - In a spectacularly creepy scene near the end, John gets to fulfil his fantasy of embalming a loved one, complete with this.