The book opens up with a helpful recap of the previous one's story hooks and plots, which I believe more books should include. The previous Melokai is dead along with her child, the rebellion by the peons has been crushed, and the people of Peqkyrian are stuck between the twin dooms of death or losing their traditionalist Amazon-esque culture. Worse, they are surrounded by enemy civilizations that wish to destroy them for their alien ways as well as resources. The Peqkyrian are not perfect victims with a history of conquest, slavery, and oppression among them.
Much of the book's first half deals with following up the events of the previous one's climax. The Peqkyrian have been hit hard and are struggling to deal with the blow to their cultural pride every bit as much as the damage done by the invaders. Though they technically won, they had their leader killed and their great library burned to the ground. Rayma's death causes most of the people to mourn her, even though she was a hated tyrant just a few days prior.
Violya is the new Melokai and stuck with the unenviable task of trying to reform a society that murders most of its useless men, keeps slaves, and is corrupt with cronyism at every level. She has the power of the Sight and has won a great series of victories but this does not guarantee her status. Violya wishes to reform Peqkyrian society, if for no other reason than their rampant slavery and misandry deprives them of valuable military resources. Unfortunately, reform is not always welcome and has the potential to backfire as we see with other rulers.
I was particularly fond of the character Jessima. Married off to a religious fanatic who she is not overly fond of, she's carrying the baby of his brother and set to become queen of Lian. Unfortunately, it is a society with no respect for women and she is expected to be nothing more than a pampered concubine when the entirety of the royal dynasty comes apart around her.
The politics of this world are brutal, the action is fierce, and the world-building is top notch. I think if you're looking for a new grimdark series then this is probably your best bet. It has a female perspective that is sometimes overlooked in the genre but benefits works like A Song of Ice and Fire as well as The Witcher. Sometimes the characters are a little too unsympathetic but everyone's of enjoyment for antiheroes varies.
I was also fond of the characters Ammad and Toby as the two of them show very different perspectives on the non-Peqkyrian storylines going on. Ammand is a brutish murderous scumbag who is like Khal Drogo and Joffrey had a baby. He has nothing going for him but his ability to kill and royal pedigree. So, when he loses both of his arms, he has nothing to fall back on. Toby is a captured prince who is tortured by the depraved ancient enemies of his family who have no interest in leaving him intact for ransom. His horror story is similar to the adversity many women suffer in grimdark fiction and seeing it gender reversed was, if not refreshing, an interesting twist.
In conclusion, definitely check this out if you have the time. In the Heart of the Mountains is shaping up to be solid works of fantasy and original to boot. I really enjoyed this book. I should warn readers that there is a lot of dark subject matter within. At least one character suffers sexual assault, there is torture, and it is a dark violent world that absolutely deserves the title of grimdark. It is also a strongly feminist work that I think brings a new view to the genre.