Empire of Storms is the fifth novel in the Throne of Glass series by Sarah J. Maas. This is officially the second-last novel in the series (if you don't include the prequel novellas, and the novel in Chaol's perspective).
What it's about:
After the King of Adarlan's death, Dorian is now king - but that doesn't mean the fight is over. In fact, now even more questions have arisen. Grieving his father, and coming to terms with the magnitude of his powers, Dorian isn't fully ready to rule. Aelin, ready to reclaim her throne, sets off to Terrasen. But Aelin hasn't been heard of for years - is her kingdom ready to have her as their queen? And what of Duke Perrington? Or have his forces in Morath grown too strong to be stopped?
After the King of Adarlan's death, Dorian is now king - but that doesn't mean the fight is over. In fact, now even more questions have arisen. Grieving his father, and coming to terms with the magnitude of his powers, Dorian isn't fully ready to rule. Aelin, ready to reclaim her throne, sets off to Terrasen. But Aelin hasn't been heard of for years - is her kingdom ready to have her as their queen? And what of Duke Perrington? Or have his forces in Morath grown too strong to be stopped?