At another level, however, the structure of The Luminaries is based upon astrology. Yes, astrology. But the tome is far more complex than Mystic Meg?s column. Catton used charts from Sky & Telescope and a software program called Stellarium to plot the stars and planets during the course of when the narrative takes place, with characters linked to the heavenly bodies. There are 12 ?stellar? characters who correspond to the Zodiac signs and seven ?planetary? characters, all grounded by the ?earth? character, Crosbie Wells, the murdered man whom the mystery revolves around.

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She was delighted to discover a ?triple conjunction in Sagittarius, three planets in the same sign? around the time she had been planning to set the novel. ?As I tracked it over the year, I could see that certain planets were following each other and it set me to thinking about how I could put that into a story. Mercury, which is a planet that governs reason, was following just behind all the other players of the action. So I could build this narrative that the person who is trying to unravel the mysteries is one step behind it all.?

She pauses and laughs. ?It sounds a bit mad, I know. Astrology started off as an intellectual curiosity but it has become something more and I?ve gotten slightly obsessed. This is my first interview for the book and I?ve been wondering how much I should talk about astrology without sounding crazy. And I?ve been forbidden from talking about astrology by many of the people in my personal life.?