Antonia; or, The Fall of Rome - Wilkie Collins

Enter Big Willy C. In this his first published novel, Collins tackles two conflicts in the Rome of 408 AD: Paganism vs. Christianity and the titular hero, the daughter of a Christian Roman zealot, Antonia vs. Goisvintha – a Goth survivor of a Roman massacre. And when mild-mannered Antonia ends up captured by Goisvintha's brother during a siege, a tale of betrayals, sex and cat and mouse can truly unfold. It's not giant mech battles on distant planets exactly, but for 1850 English literature, this is pretty darn exotic.