The Buried Giant isn't what you'd expect. Sure, it's medievalist fantasy, but it's not A Game of Thrones or even Wolfskin. Ishiguro uses the trappings of medievalist fantasy to explore the nature of memory, history, and relationships in an almost surrealist way. There's no blood and thunder here. There's not really much action, and a good amount of what action there is happens off-page and is related through the characters' discussion and memories of the event. 
 Memory is one of the major themes of the novel. What happens to us if we don't have our memories? What happens to our relationships? Not only does he explore personal memory, but cultural, historical memory. What if things aren't the way our culture remembers them being? As a medievalism-ist, I relate to that last one pretty strongly; my whole wheelhouse is "the medieval period isn't what you think; it's been completely reconstructed for you (several times, actually) by cultural desires, needs, and myths." 
 The style of the novel has a dreamy sort of quality that reminded me of The King of Elfland's Daughter, which actually places it in more of a classical fantasy style than a more modern, action-focused fantasy style. For people not used to that, I can see the novel being deeply confusing, confounding, and even frustrating, but if you suspend your expectations and go into it with an open and analytical mind, you'll get a lot out of this book.