The Noughts & Crosses series is set in a world where the people with black skin (Crosses) are dominant over the white people (noughts). The title is a reference to the game known in Britain as "noughts and crosses" and in the United States as "tic tac toe", where O represents a nought (or blanker) and X a cross (or dagger); adjusting this to an American audience would negate the pun on 'nought'. The books use first person narration, with the narrator alternating between chapters, and an X or O before the narrator's name indicates their race. Dual heritage Callie-Rose is represented by an O and X combined.

Apart from the obvious inversion, the books' world is quite similar to early 21st century Britain but racism and prejudice are much more overt, with resemblances to apartheid in South Africa. The series tells the story of several characters from two interlinked families with very different positions in society.

It can be compared with Shakespeare's Romeo and Juliet in that the two leads—Sephy and Callum—"shouldn't" be in love because they are of a different skin colour, in the same way that Romeo and Juliet belong to two feuding families Montague and Capulet.