Excited to be going back to the world of Antarktos! Although this book can be read as a stand-alone, I highly recommend reading Antarktos Rising and, one of my all time favorites, The Last Hunter.
This is the story of Solomon's daughters, Aquila and Norah, as they learn to fight and survive the underground realm of Antarktos when Aquila is taken by the Nephilim, who want to turn her into a hunter. Norah must overcome her fear of inadequacy in order to save her sister and on the way, learn about her amazing power.
Highly recommend (the whole series)!