Mary Stewart

Six of Crows by Leigh Bardugo
Ketterdam: a bustling hub of international trade where anything can be had for the right price—and no one knows that better than criminal prodigy Kaz Brekker. Kaz is offered a chance at a deadly heist that could make him rich beyond his wildest dreams. But he can't pull it off alone...

A convict with a thirst for revenge
A sharpshooter who can't walk away from a wager
A runaway with a privileged past
A spy known as the Wraith
A Heartrender using her magic to survive the slums
A thief with a gift for unlikely escapes

Kaz's crew are the only ones who might stand between the world and destruction—if they don't kill each other first.

And I Darken by Kiersten White
No one expects a princess to be brutal. And Lada Dragwyla likes it that way.

Ever since she and her brother were abandoned by their father to be raised in the Ottoman sultan’s courts, Lada has known that ruthlessness is the key to survival. For the lineage that makes her and her brother special also makes them targets.

Lada hones her skills as a warrior as she nurtures plans to wreak revenge on the empire that holds her captive. Then she and Radu meet the sultan’s son, Mehmed, and everything changes. Now Mehmed unwittingly stands between Lada and Radu as they transform from siblings to rivals, and the ties of love and loyalty that bind them together are stretched to breaking point.

The first of an epic new trilogy starring the ultimate anti-princess who does not have a gentle heart. Lada knows how to wield a sword, and she'll stop at nothing to keep herself and her brother alive.

The Crystal Cave by Mary Stewart
Who was Merlin? Was the famed magician of Camelot & King Arthur's court really a sinister, all-powerful being from another world? Was he truly a Prince of Darkness? Or was he a man with the passions of other mortals? A man with unique intelligence & unusual gifts? Why was he so feared? How did he come by his occult powers? Why was the crystal cave so important to him?
5th century Britain is a country of chaos & division after the Roman withdrawal. Born the bastard son of a Welsh princess who will not reveal to her son his father's true identity, Myridden Emrys--or as he would later be known, Merlin--leads a perilous childhood, haunted by portents & visions. But destiny has great plans for this no-man's-son, taking him from prophesying before the High King Vortigern to the crowning of Uther Pendragon & the conception of Arthur--king for once & always.