* AdaptationDisplacement: Averted. Many people do not know about the stage version, even though it ran for a long time and got a thumbs up from the author.
** At the end of the book, [[spoiler: Sephy and Callum confessing to each other that they love each other as he is hanged.]]
** The eventual reconciliation between [[spoiler: Sephy and Callie at the end of Checkmate]] is truly beautiful.
* MoralEventHorizon: [[spoiler: Jude's murder of Kara]]. Possibly he himself considers it to be this, as he is notably more heartless afterwards, and much as he suppresses his conscience, it's clear that he never forgives himself for it.
* NarmCharm: When Jude tells Cara that nought women often try to look like Cross women. He has a point, but then he tells her that they can buy panties which are padded so they can have more curvy hips, it just becomes funny. But still sad.
** [[spoiler: Callum's hanging]]
** Much of Callie Rose's childhood counts as this, to the point that she is talked into [[spoiler: becoming a suicide bomber while still a child.]] It is chillingly believable that she could be driven to this by the hell of her upbringing, and the manipulations of [[spoiler: her uncle.]]
* WhatDoYouMeanItsNotForKids?: The series is targeted at Young ADULTS, and should not be read by anyone under 13. Still does not stop parents buying them for a 10 year old then complaining.
* TheWoobie: Callum to an excruciating degree.