Well, personally I love it because it:

a) is very character-driven,

b) allows its protagonist to be both earnest and genuinely good without the narrative cynically punishing him for it, despite taking place in the sort of court intrigue setting that is usually rife with that sort of grim cynicism. someone else described it as “hopecore,” which I kinda love

c) has enough fantasy worldbuilding background that it feels like it’s taking place in a fully-fledged and unique setting, not a standard Tolkien and/or DnD knockoff, but doesn’t let itself get bogged down in the minutiae. 

d) (extra props for, despite being technically steampunk (gas lighting, dirigibles, and factories exist) not being either really goddamn annoying about it or forgetting that it’s not just adding decorative gears and unnecessary goggles to things: the country is in the midst of its industrial revolution, with all the grimness that goes along with it, and that doesn’t get ignored (admittedly, the POV character is the actual goddamn emperor, so is pretty sheltered from all the grimness, and also uh… is royalist kinda by default, but the issue is brought up and treated seriously by the narrative).)

e) has elves (etc) express their emotions with ear movement as well as our familiar human body language, which is a surprisingly charming touch and very… vivid. 

f) (actually all the descriptions are very vivid, I had fully-formed mental pictures of… everything… for most of the book, and I’ve wanted to draw it all.)

g) has correct and non-gratuitous use of “thou” as the familiar second person singular.

h) …listen, the protagonist is a darling, oh my god he needs about ten hugs, read it so you’ll want to hug him too.