It is one of only a handful of Connelly novels that features neither his main protagonist Harry Bosch or his secondary protagonist Mickey Haller. Instead the hero is Terry McCaleb, a former FBI agent who used to hunt serial killers. "Former" and "used to" because McCaleb suffered a heart attack while still in his mid-forties and eventually had to have a heart transplant.
Retired from the FBI due to his disability, McCaleb runs a charter fishing business in the waters around Carrillo Marina in Los Angeles harbor. One day he is approached by Graciela Torres, who tells him some shocking news: her sister Gloriana Torres was the person who donated the heart, and the heart was only available because Gloriana was murdered during a convenience store robbery.
Graciela asks Terry to do what the cops can't, namely, find her sister's killer. Terry takes the job reluctantly, as it has been barely two months since he was released from the hospital following transplant surgery. He soon finds a far darker crime than he suspected, one which has a surprising connection to him.
In 2002 Connelly's novel was adapted into a film, also called Blood Work, featuring Clint Eastwood in his last action movie role. Connelly brought back the Terry McCaleb character in A Darkness More Than Night, in which McCaleb is teamed up with Harry Bosch.
- AB Negative: Turns out to be the solution to the mystery. The killer murdered Gloriana Torres because 1) she had the same rare blood type as McCaleb and 2) she was an organ donor.
- Asian Store-Owner: The store owner where Gloria Torres is killed is named Chan Ho Kang. He gets killed too; Terry later commiserates with his widow.
- Chekhov's Gunman: James Noone, the witness at the Cordell shooting whom Terry hypnotizes, turns out to be the murderer.
- Continuity Nod: This novel is established as being part of the wider Michael Connelly universe by mentioning the Poet investigation (that's The Poet) as well as reporter Keisha Russell, first mentioned in Harry Bosch novel The Last Coyote.
- Donut Mess with a Cop: Terry makes sure to bring a box of doughnuts when visiting the Torres homicide cops, as a means of ingratiating himself with them. It isn't a very successful tactic.
- Double-Meaning Title: Blood Work refers both to Terry McCaleb's medical issues and his old job hunting serial killers for the FBI.
- Dream Sequence: Terry has a nightmare in which he's the one who gets shot in the convenience store.
- Early-Bird Cameo: Terry, who is in pretty deep trouble, sees an ad for a lawyer, one Michael Haller Jr., and briefly considers calling him. This is Mickey Haller, who first appeared seven years later in The Lincoln Lawyer and has been the protagonist in six Connelly novels. It's also a Continuity Nod since the second Harry Bosch novel, The Black Echo, established that Michael Haller Senior was Harry's father.
- Enhance Button: Used relatively realistically via pixel guesswork to enhance the video from a convenience store security camera.
- "Eureka!" Moment:
- Terry figures out the link when he sees a blood drive sticker at Gloriana's place of work and realizes that she and Cordell both gave blood.
- Terry figures out that James Noone was pretending to be under hypnosis when he realizes that otherwise Noone would have responded to Jaye's words instead of only his.
- Evil Stole My Faith: Terry "was long past believing in God," because of all the horrible things he saw as an FBI agent chasing serial killers.
- We find out in A Darkness More Than Night that he regains his faith.
- Foreshadowing: Several times in the first part of the novel, the Code Killer case is mentioned as one of the serial killer investigations Terry worked on.
- Houseboat Hero: Terry lives on his fishing boat, which he uses for a charter business.
- It Works Better with Bullets: At the end, Noone breaks into McCaleb's room and steals his gun, which he later uses to threaten McCaleb with. What Noone doesn't know is that it was McCaleb's habit to carry his weapon without a round chambered. McCaleb, however, has Noone's gun, which Noone had planted on McCaleb's boat as part of the frame, and Noone's gun DOES have a bullet in the chamber.
- Kirk's Rock:
"The slanted and jagged formation caused by tectonic upheaval was beautiful in the afternoon light. The sun was hitting the front rock faces at a low angle and throwing the crevices into deep darkness. It looked beautiful and dangerous at the same time."
- The backstory recounts how detective Jaye Winston had investigated the case of a murder victim found at "a large outcropping of sandstone known as Vasquez Rocks." This is how she got to know McCaleb, who now needs her help investigating another murder.
- Later McCaleb passes by the rocks again and thinks about them.
- Not With the Safety On, You Won't: McCaleb, being held at gunpoint by Noone with his own weapon, employs a variant of this by pointing out that his gun isn't loaded. McCaleb's habit was to carry the weapon without a round in the chamber, and Noone never checked it.
- Obfuscating Stupidity: At the end, McCaleb plays dumb about the killer's fate, pretending to be hearing about it for the first time from Winston. Whether Winston buys it or not is left open to interpretation.
- The Only One Allowed to Defeat You: A variant of this trope. The Code Killer doesn't want McCaleb's heart failure to take him out of the game, so he gets McCaleb a heart.
- Pink Mist: The novel describes "a horrifying mist of blood" spurting out of both the entry and exit wounds in Gloria's head.
- Pre-emptive Declaration: After Terry tells the FBI agents that they can't come on his boat without a warrant they don't have, one of them says "We didn't need one after you gave us permission to enter and search." The FBI guy is moving to the door when Terry points out that 1) the door is locked and 2) Buddy Lockridge is watching everything from his boat.
- Psychic Link: Terry is puzzled when Graciela Torres looks familiar. Apparently it's the heart.
- Serial Killer: The Code Killer, one of the cases Terry investigated, turns out to be the murderer.
- Buddy the mystery aficionado is reading a Japanese mystery novel called Inspector Imanishi Investigates, which is totally real. Later on Buddy is reading Death of a Tenor Man, another real novel.
- “Is it safe?” McCaleb asked, remembering the line from a movie he had enjoyed some years before.”
- The killer has a ritual of saying "Don't forget the cannoli" right after murdering someone, a line taken straight from The Godfather.
- Shown Their Work: In the book, McCaleb's explanation of the DRUGFIRE computer and its origins.
- Also, a lot of details about the after-care necessary for a heart-transplant recipient.
- The 'Verse: The novel joins Connelly's established one by mentioning The Poet, Serial Killer bad guy of Connelly's novel The Poet, and also containing other references to the Harry Bosch universe, such as L.A. Times reporter Keisha Russell, introduced in The Last Coyote, Joel Bremmer, the killer in The Concrete Blonde, and FBI agent Rachel Walling, introduced in The Poet. Mentioned in passing is Michael Haller, Jr., who we will come to know later as Mickey Haller, The Lincoln Lawyer.
- Worthy Opponent: The Code Killer actually uses the phrase "worthy opponents" to describe himself and McCaleb. Terry does not reciprocate, not at all.