The Dark Half

The Dark Half is a novel by Stephen King.

Thad Beaumont is a novelist who writes thrillers under the pseudonym of George Stark. As he moves on with his career, he begins using his real name and puts the pseudonym to rest, going so far as to hold a symbolic funeral and erect a headstone for the late Stark. Not long afterwards, someone with Thad's fingerprints and going by the name of George Stark starts killing people...

The Dark Half provides examples of:

 * Arc Words: "The sparrows are flying again."
 * Author Avatar: Thad Beaumont, to an extent. Stephen King has written (and still does, occasionally) under the pseudonym of Richard Bachman, and he treats Bachman like a separate person, even giving him a separate biography in Bachman novels. He wrote The Dark Half partly to explore that idea in a literal sense.
 * Bittersweet Ending: Stark is destroyed, but it's revealed in Needful Things that the psychological scars left by the ordeal drove Thad to drink and ruined his marriage, and eventually he killed himself.
 * Blondes Are Evil: George Stark
 * Body Horror: Stark's body as he "loses cohesion" starts to decay and rot.
 * Clueless Deputy: Norris Ridgewick.
 * Dragged Off to Hell:
 * Enemy Without: This should be self-explanatory.
 * Evil Smells Bad: A policeman inspecting the car George Stark had used earlier notes that it smells hostile and animalistic. Stark also falls into this trope later in the book, being followed by the stench of his own decaying body.
 * Evil Twin: If Stark was really Thad's vanished twin, he could be considered this.
 * Eye Scream: During Thad's childhood his foetal twin begins to regrow in his brain including an eyeball and several teeth. A surgeon lances the eyeball and extracts it. Cut to the future where the Thad is an author writing crime fiction about a character who -- you guessed it -- lances someone's eyeball with a paperclip.
 * Impaled Palm: Stark at one point makes Thad stab himself through the hand with a pencil. See Poke in The Third Eye.
 * Grave Humor: Stark's headstone reads "Not A Very Nice Guy".
 * Groin Attack: George Stark combines a old fashioned straight razor, an upward slashing attack, and the groin of an unfortunate cop. All described with typical King skill. Did you just wince? Imagine reading it.
 * Madness Mantra: "The sparrows are flying again"
 * Knife Nut: Alexis Machine, the antagonist of Machine's Way and Riding to Babylon, prefers to use a straight razor to kill his victims.
 * Most Writers Are Writers: Thad Beaumont, obviously.
 * Obfuscating Stupidity: Thad's colleague, Rawlie De Lesseps, at first appears to be nothing more than an absent-minded professor. Actually, he is very knowledgeable about folklore and literature and helps Thad to uncover the mystery behind the phrase, "The sparrows are flying again."
 * Painting the Fourth Wall: Like a few other of King's books, some parts appear as actual handwriting instead of the typed font.
 * Poke in The Third Eye: Thad has a telepathic link to Stark, and in one scene he tries using it to get information from him. It doesn't end well.
 * Psychopomp: The sparrows, mentioned by name.
 * Reasonable Authority Figure: Sheriff Pangborn. After Stark leaves a bloody fingerprint perfectly matching Thad's at a crime scene, Pangborn arrives to arrest Thad. But when Thad produces an ironclad alibi, Pangborn believes him and does all he can to help catch Stark.
 * Rise From Your Grave: Stark manifests himself by digging out of his fake grave.
 * Roaring Rampage of Revenge: After Stark is "killed", he begins to exact revenge on everyone he views as being responsible for his death.
 * Serial Killer: Alexis Machine, the arch villain of George Stark's crime novels, is one of these.
 * Shoot the Shaggy Dog: Some see the story as this in light of what happens to Thad afterwards (See Bittersweet Ending).
 * Split Personality: George Stark started out as this.
 * Slashed Throat: Stark uses a straight razor to slash his victims' throats.
 * That Man Is Dead: Played with and subverted when Thad has a mock photo shoot in front of Stark's grave.
 * Twin Telepathy: A plot point.
 * Viewers Are Geniuses: An in-universe example. The protagonist has written several highly intellectual novels with great reviews and poor sales. In the meantime he has also written under Stark's name intentionally trashy books that engorge themselves on sex and violence which have gone on to become bestsellers. King wrote the book in part as a response to his own pen name Richard Bachman becoming public knowledge. The stories he wrote under the pen name in turn tended to be less psychological than those with his own name on them.
 * Villain Protagonist: Alexis Machine in Stark's books.
 * Vomiting Cop: When Norris Ridgewick finds one of Stark's victims, he throws up, but manages to avoid the corpse.
 * You Do NOT Want to Know: One of George Stark's murders is so gruesome that King leaves it completely to our imagination (when Liz is asked if she wants to know how the victim met her end, she immediately says "No").