The Splintered Princess

A magic dagger. A beautiful man. And me.

We were a match made to be destroyed.

The dagger lured me in with whispers: I was meant to be an empress, not a farm girl, simple, sequestered and common.

Daring to dream of power and love, I picked the dagger up.

And I reached for him.

Avid and ardent, we were both vicious in strength and feral at heart. But he protected those he loved while I—heedless, rash, slapdash with my emotions—played carelessly with the lives and hearts around me.

But others played better.

My country's overlord kidnapped my family and forced me into a charade: be a decoy princess to protect his queen.

My weapons trainer hid his true agenda as he taught me to fight with sword and dagger, to identify poisons, to ingest them, and to sever my soul.

Even the spirit of the man I loved suppressed a secret savagery behind his charm.

But his spirit, split from his body, was no equal for his physical form. Captured by the enemy and warped into an atrocity, his true self made our love a battlefield… strewn with a thousand downfalls… one for every time I defied him.

NOTE: This book is not a fluffy, written-for-tropes, quick-and-fun fantasy romance. No one's survival is guaranteed except the endgame romance, which you might or might not discover in this book. At the end of this book, one of her potential loves will die, one's survival is debatable, and one will live to torment her...
Things will end up fine at some point, but first she's going to go through some sh*t, and she's going to get mad. Go in prepared.
This is also not YA. Despite the heroine being 16 at the beginning of this book, she ages up as the series progresses till she's in her 30s.