Martin Green 
The Plastic Empire [EPUB ebook] 

In an alternate reality a technologically advanced Roman Empire has developed the plastic people; robots with souls. Angered by their creation, the Pope crusades against The Empire’s border city of New Constantinople, capturing the emperor’s favourite plastic person. With the brutal interrogation of the plastic person looming, the emperor calls upon the Green Man of ancient Pagan folk lore to rescue her, before she reveals the secrets of Rome. Treachery, strangeness, and betrayal abound in this fantastical tale of magic and technology.