I like it. It sets the scene, introduces the major players and the premise right off the bat. Lets the reader know what to expect (but not too much!)
Mine could probably do with a bit of shortening too
"Three years ago, all things ended.
Fire rained from the sky, bringing with it horrors that thrived in the slaughter and destruction, a predator unrivaled that hunted humanity almost to extinction in mere months.
But all was not lost. An island haven, remote and isolated, survived and with it a few hundred refugees who have since managed to eke out a living in this dark time after civilisation, far from the ruins of the old world and the beasts and ghosts that dwell there.
Now a new threat emerges, an old power resurgent, and one young woman must fight with everything she has for everything she holds dear with (or in spite of) whatever help the capricious gods might provide.
It is now she must decide if freedom is worth the ultimate cost: her life."