The cover takes imagery presented in the book, and is laid out in a manner which is intended to mirror the often cryptic narrative of the story; the cover remains eyecatching and engaging even though the design as a whole is only fully revealed when viewed from every angle, much in the same way that plot elements are hinted at within the book, before later being expanded upon and pieced together.
The Penguin logo itself serves as the only source of colour on the entire cover, and was kept that way intentionally to allow the orange to stand out, as the novel notes that orange is the colour representative of insanity (another theme touched on by the author).