Dark romance. Neighbors. The anti-heroine is a killer and hero is a geek/nerd.

All I remember is a scene from the beginning of the book. The H and h are neighbors. The H is a gamer/nerd that lives in an apartment and has a pretty solitary life, the h is a serial killer that just killed a man in her apartment. So she rolls up the body in a rug and carries it through the hallway, she's very small so she's having a hard time, then the H opens his door and salutes her and offers her help, but she's nervous 'cause the blood is starting to sip on the floor.

I remember the guy likes to play a computer game akin to SIMS, he starts chatting with a girl there.