Anonymous Killer Narrator

This trope is frequently seen in modern day Mysteries and Thrillers.

In between the regular narration of the book that features the detective trying to figure out the case, there are sometimes chapters written from the perspective of the serial killer. These chapters usually are written anonymously and/or gender neutral so as to disguise which of the known characters in the book it is that is doing the killing, but most of the time it's fairly clear that the anonymous pervert is male. Is also frequently The Peeping Tom.

These chapters frequently describe in great, loving detail how much they lust after the heroine (or other target) and can't wait to fuck/torture and then kill them. They also give detail as to what information the killer has on the investigators on the case.

Literature

 * Lost Souls by Poppy Z. Brite
 * The Healer by Frank G. Slaughter
 * Pretty much every Jeffrey Deaver book has these.
 * The Spenser novel "Crimson Joy" has one, not usual for the series.
 * The "I will be called a murderer" chapters of Orhan Pamuk's My Name Is Red.
 * "Stone Cold" by Robert Swindells contains paragraphs written from the perspective of the murderer, Shelter.
 * Dialogues of the Dead from Dalziel and Pascoe, a series of novels by Reginald Hill.
 * The Surgeon, first book of the "Rizzoli & Isles" saga by Tess Gerritsen has interludes with the killer's thoughts.
 * The Hercule Poirot story "The ABC Murders", explicitly marked as not being from Hastings' narrative.