Basically, this book takes high fantasy tropes and screws with them. This is not a parody; it's not so facile. But the author has clearly read and loved a great deal of fantasy in his life, and knows the basic stories well. And when he grew tired of the easy answers and Light vs Dark epic battles, he created this.
The elves have left Middle Earth--but they were actually aliens, driven half-mad by their flight across the stars, and the half-Elven Princess they leave behind them is a black lesbian with a drug problem. (I found Arceth to be the most fascinating character of all. Her eldritch family taught her modern concepts of morality, but she's been stuck in a feudal society for hundreds of years--her high-minded ideals are beginning to wear thin.)
The "elves" also left behind a magical sword, wielded by war hero Gil. Like many war heroes in fantasy novels written lately, Gil has become a washed-up mercenary, only pulled back into the Epic Battle for Civilization by the danger posed to a long-lost female loved one. But uh, Gil is gay, and his main resistance to helping is that the *last* Epic Battle turned into a slaughter of civilians, and his city tortured his lover to death before his eyes.
His former sword-brother, the barbarian Egar, is also pulled into the fray. Egar is a great play on the usual "savage tribe" trope.
This book is not a criticism of High Fantasy--it takes it to the next level. The queer characters, the characters of color, the atheists, the questions of consent and privilege, the logical next step for a country that's just defeated their Big Foe...Morgan uses all of it. And the adventure is better for it.