Published under DC Comics’ DC Graphic Novels for Young Adults imprint, the novel is a retelling of Cassandra Cain’s origin for new audiences. Once a trained killer under her father, Cassandra turns her back on him after her latest killing causes her to have a change of heart. Having nowhere to go, she takes up residence in Gotham Library and makes new friends as she seeks to learn about Gotham’s vanished hero, Batgirl. However, once she sees her father on the move, Cass decides that if she’s going to protect her new friends and home, she will have to become a hero herself, even if that means having to face her own self-doubts.
Shadow of the Batgirl provides examples of:
- Abled in the Adaptation: Cass’s initial inability to speak is presented here as less of a neurological impairment, so much as simply her lacking the education and language exposure to speak and read. Once she starts hearing people speak and attending Barbara’s reading classes, Cass picks up both skills rather quickly.
- Abusive Parents: Not only is Cass's dad still as terrible as ever in this adaption, but new character Jackie had a father that forced her sister and her to constantly compete against one another.
- Adaptational Distillation: As mentioned below, Batman doesn’t play a role in this story, whereas in the original comics, he was quite important to both Barbara and Cass’s origins. The Killing Joke, which led to Barbara’s crippling, is also not mentioned and instead it’s implied that she was in a much more mundane accident.
- Adaptational Early Appearance: Barbara’s Batgirl outfit is shown to be the Burnside version of her outfit which she wore Post-Flashpoint after her initial (and more traditional) suit had been destroyed. But, the Burnside costume only appeared after in-universe years of Barbara having been Batgirl, then Oracle, and back to Batgirl again. Here, Barbara's Burnside outfit is shown to be what she wore prior towards becoming Oracle, instead of the other way around.
- Adaptational Nice Guy: Barbara is much kinder and more patient with Cass this time around, and has had much of her abrasiveness made to be non-existent.
- Adapted Out: Bruce/Batman isn’t even hinted to exist in this universe, and Word of God outright confirms that he doesn’t. Instead Barbara is shown to have been Gotham’s only major vigilante up until she gave it up. Presumably, the same is true of the Joker as Barbara doesn’t mention or hint towards him when explaining her origin to Cass.
- Adaptational Villainy: Cass in this universe has killed several times before her redemption, and only stopped, and initiated her redemption, because she heard her last victim say the word "daughter". This is in contrast to her mainline counterpart, who stopped killing after the experience of her first kill was extremely unpleasant for her.
- And the Adventure Continues: The book ends with Cass taking up the mantle of Batgirl and fighting crime alongside Barbara (in the role of Oracle) and Jacqueline.
- Beta Outfit: When Cass first decides to become Batgirl, she makes a costume out of clothes and supplies she can find in the library, as well as out of the outfit that Jackie gave her.
- Big Bad: David Cain is the main antagonist as throughout the book his organization attempts to search for and capture Cass, culminating in a final showdown that sees Cass defeat Cain and all his minions in the library.
- Canon Foreigner: Jacqueline and Erik are two characters entirely original to this novel who play major roles in Cass’s origin story here.
- Character Exaggeration: While his more abusive actions towards Cass are glossed over here in order to appeal to younger audiences, David is as a whole more one-dimensional as a character here as his complex relationship with Cass is pushed aside in order to focus on Cass and her self-growth outside of him.
- Cool Old Lady: Jacqueline is this as while she’s an older woman, she knows how to fight and immediately gives free food to Cass after she finds her eating garbage. Later on, Jacqueline hands down her old, but really fashionable, clothing to Cass, gives her advice, and even takes her in by the end. Jackie is also good friends with Barbara and even knows the latter’s former identity as Batgirl. She's even cool enough to directly join Barbara and Cassandra in fighting Gotham's latest crime wave.
- Dark and Troubled Past: Cass, who was trained from birth to kill, only stopping at the beginning of the book.
- First Kiss: Cassandra has hers with Erik.
- Gadgeteer Genius: Barbara makes her own gadgets and computer programs and even decides that she prefers doing those things compared to actually being Batgirl.
- If You Kill Him, You Will Be Just Like Him!: After having defeated him and his whole organization, David Cain tries to get Cass to kill and take control of his group, as he had always intended for her, but she refuses since that would make her into something she doesn’t want to be.
- Lighter and Softer: Almost literally thanks to the art style, which has much brighter colors and cartoonier character and set designs compared to Cass’s original comics. This can be especially seen when one compares Cass’s costumes here, compared to what she has worn in the original universe. Gotham itself looks much brighter, as it's mostly shown in the day here.
- Missing Mom:
- While Cass’s mother is not shown in the book, she's implied to still be Lady Shiva as while Cass doesn’t know much about her, she does know that she likely isn’t a good person. Though on the positive side, the Japanese-American Jackie is able to deduce that Cass, through her mother, is Chinese-American and uses their shared Asian heritage to connect with Cass.
- Barbara’s mom is also implied to have died in this universe, like in the main universe, but she plays a significant role in Barbara’s motivations and origin here.
- My God, What Have I Done?: Cass has this reaction after breaking Erik’s arm after she mistook him for one of her father’s henchmen.
- Parental Substitute: Barbara to Cass as in the main universe, but also Jackie towards her as well. Indeed, as Jackie essentially provides food, a bath, clothing, and by the end an actual home for Cass, she is likely a more direct example here then Barbara is.
- Strike Me Down with All of Your Hatred!: David tries to encourage Cass to kill him so she can become what he always wanted her to be. She refuses, instead having him arrested.
- Tyke Bomb: As in the main universe, this is Cass’s origin, and much of the story is about her trying to grow out of that role and be a hero. She actually spends much of the novel trying to resist the impulse to kill that was forced into her by her father. Whether it be resisting to kill a mouse or trying to avoid hurting those who try to touch her, even though her instincts tell her to respond violently.
