"The Heart of What Was Lost" is a high fantasy novel written by Tad Williams, published in 2017, and serving as a sequel to his Memory, Sorrow and Thorn trilogy. Directly after this book, Tad Williams started releasing books from another trilogy, set far in the future, with this book being a bridge of sorts between the two trilogies.
This novel takes place almost immediately after events at the end of the final book of the Memory, Sorrow and Thorn trilogy. The armies of the humans and Sithi (the general equivalent to high fantasy elves in the trilogy) have just routed the armies of the Norns (basically dark elves, only pale white). This book follows one human army, composed mostly of the world's equivalent of Vikings, as they pursue and besiege the Norn armies. The book is told from two points-of-view: two young mercenaries in the human armies, and some high lords and ladies in the Norn armies. The military campaign is a grinding, violent affair where the humans wish to revenge the atrocities of the Norns, while the Norns wish to defend their culture against what they see as something basically one step above animals. The Norns, previously interchangeable fantasy villains, are presented as having a culture of their own, deep in tradition, although also arrogant and violent.
Although I don't know how intentional it was, the book struck me as having historical parallels to the last days of Japan during World War II, as a traditional culture based on loyalty to a royal figure is faced with defeat by a culture that they think of as hopelessly inferior. Of course, since this is only true in broad strokes, I wouldn't read too much into it.
The thing that struck me about this book the most was the tone. This book is set in the same world of Osten Ard as the previous trilogy, with the same characters and setting. But externally, in the author's time, twenty years had passed, and trends in fantasy had changed considerably, especially with the television success of Game of Thrones, which itself took some of its concepts from Memory, Sorrow and Thorn. And this book feels like it took a lot of inspiration from Game of Thrones: while the earlier trilogy had the buoyancy of a fantasy romance, this book drags through the grind of siege warfare. Maybe it was me as a reader, rather than the author's intent, but I just couldn't quite read this book with the easy optimism of the 1990s that seemed to flow through Memory, Sorrow and Thorn.
In what is perhaps a silly comparison, reading this book was like listening to a solo album by an ex-Beatle: the creativity and ability were there, but the tone, the texture just can not be recreated. It doesn't mean there is something wrong with this book: it just shows how much things have changed in the past two decades, and that even in a fantasy novel, the zeitgeist of the outside world creeps in unexpectedly.