Grace of Kings has been referred to as an Asian Game of Thrones (by Wes Chu, in the reviews at the beginning of the book. I think he's right on.
If anything, it's really more Game of Thrones than Game of Thrones--but fewer characters and a lot less blood. Otherwise, the parallels are very strong. The speculative elements are not highly important in either series, though I'd say they are barely even present in Grace of Kings. The main drivers are the protagonists--and Liu has the skill to manage two of them.
We have Kuni Garu, a carouser and gangster with a heart of gold, and Mata Zyndu, a man born royal in every sense of the word--noble birth, and a giant (eight feet tall). They work together to overthrow the ambitious and cruel Emperor Mapidere, who unified Dara with blood. Once they succeed, sad and somewhat predictable things happen. Politics is a hard thing.
Ken Liu is an excellent writer, so the story was not difficult to read. One feels for the characters as they succeed and suffer. But I guess I'm something of an outlier in that while I like A Song of Ice and Fire (haven't seen the TV series), I don't think it's going to be a series for the ages in the fantasy genre. It's basically a soap opera. Grace of Kings is a somewhat lesser version of Game of Thrones, and suffers from the comparison. It's a nice story, but it pretty much could take place on earth, somewhere we cannot see. In a larger-than-life series like The Wheel of Time, magic and its constraints form a compelling part of the story. Grace of Kings is not larger than life--though it operates on a continental scale it is still merely life size.
For all that, I do give it 3 stars because it held my interest all the way through.
P.S. Kuni Garu is an appealing protagonist, strong when he needs to be and tender when he can be. You can't help but like him. If you enjoy your men strong and positive, I can recommend the works of Rusty Rhoad.