Very obvious spoilers ahead for Gideon the Ninth and this book.
To go from the sort of obnoxious opening chapters of Gideon, where Gideon's sense of snark comes across as forced and obnoxious, to this book where you're begging for that signature snark again is really a feat. I put GtN aside at least two or threes times before it stuck for me, but when it did, that book hit hard.
Harrow the Ninth is not an easy book, by any stretch of the imagination. All the negative reviews decrying this book as a departure from the previous one and not as fun illustrate the point of the book.
This isn't a fun book, it's a book about loss and grief. It's about what we do when we're overwhelmed by grief and try to soldier on so we'll look strong instead of coping. There's some thematic overlap here with Eternal Sunshine of the Spotless mind where Harrow is so overwhelmed with the death of Gideon so one of them could survive, and for her being the survivor, that she literally has a rival necromancer in Ianthe (both now Lyctors, sort of) do an experimental procedure to rewrite Harrow's mind and change their shared history so Gideon was never there. Instead, it was Ortus, the failed cavalier, who took her place.
Thusly, we see Harrow interacting with the remaining lyctors while carrying Gideon's longsword with her and haunted by “the body,” which is intended to be the body within the Locked Tomb she disturbed as a 10-year-old that led to the death of her family. While interacting with her fellow lyctors and ‘God,' a name named John, of all things, we see how Harrow is not considered a full lyctor because she didn't properly absorb her cavalier like the rest did.
... we know that she did, which was how she defeated Cytherea in the previous book, but in this book everything is different.
The book is split into two different narration styles. One in third, the other in second person. Yeah, that's right, a bulk of this book is in the dreaded second person. In part, because Harrow isn't telling her own story. She is being told her story.
A part of me thought “dear god, this is really going hard on this artificial memory and the allegory” because a solid 65% of this book is told like this. We don't even have glimpses of whatever the “real” is until about 60% and the final act of the book features things finally split between Harrow stuck in “the river,” a surreal part of the afterlife, while Gideon awakens and takes over Harrow's body.
While we go through this book knowing that Harrow is off, what we get a clear view of is how “God” and his lyctors work. They're dysfunctional, bitter and all hate each other, plus one named Ortus (no relation, really) is trying to kill Harrow. The mysteries unfold slowly and we spend a lot of time with the husk of Harrow knowing full well she's hurting so bad that she'd rather allow herself to be this husk of an undead immortal being than live with the guilt of knowing she lived and the only person who ever cared for her sacrificed herself to land in this position.
When Gideon “returns” it's impossible not to be excited. Think about that. I went from thinking this was the biggest piece of twee shit in the world to cheering for the return of Gideon in all her awkwardness.
By the time the book was over I ordered the hardcovers of both (I read them via library copies, more people should use the public libraries that are available to them) in a heartbeat.