[Avice]

The first 2 books in the Blackthorn & Grim series by fantasy writer Juliet Marillier (known for the Sevenwaters series and Wildwood Dancing) are discounted at Amazon US. Blackthorn & Grim is fantasy involving fairytales in Ireland with a bit of "solving magical mysteries" air, and the first book at least was quite good.

Dreamer's Pool (Blackthorn & Grim #1)
$2.99
https://www.amazon.com/gp/aw/d/B00INIJKKC/

Spoiler:

Award-winning author Juliet Marillier “weaves magic, mythology, and folklore into every sentence on the page” (The Book Smugglers). Now she begins an all-new and enchanting series that will transport readers to a magical vision of ancient Ireland....

In exchange for help escaping her long and wrongful imprisonment, embittered magical healer Blackthorn has vowed to set aside her bid for vengeance against the man who destroyed all that she once held dear. Followed by a former prison mate, a silent hulk of a man named Grim, she travels north to Dalriada. There she’ll live on the fringe of a mysterious forest, duty bound for seven years to assist anyone who asks for her help.

Oran, crown prince of Dalriada, has waited anxiously for the arrival of his future bride, Lady Flidais. He knows her only from a portrait and sweetly poetic correspondence that have convinced him Flidais is his destined true love. But Oran discovers letters can lie. For although his intended exactly resembles her portrait, her brutality upon arrival proves she is nothing like the sensitive woman of the letters.

With the strategic marriage imminent, Oran sees no way out of his dilemma. Word has spread that Blackthorn possesses a remarkable gift for solving knotty problems, so the prince asks her for help. To save Oran from his treacherous nuptials, Blackthorn and Grim will need all their resources: courage, ingenuity, leaps of deduction, and more than a little magic.

Tower of Thorns (Blackthorn & Grim #2)
$5.99
https://www.amazon.com/gp/aw/d/B00SI025PW/

Spoiler:

Award-winning author Juliet Marillier’s “lavishly detailed”* Blackthorn & Grim series continues as a mysterious creature holds an enchanted and imperiled ancient Ireland in thrall.

Disillusioned healer Blackthorn and her companion, Grim, have settled in Dalriada to wait out the seven years of Blackthorn’s bond to her fey mentor, hoping to avoid any dire challenges. But trouble has a way of seeking out Blackthorn and Grim.

Lady Geiléis, a noblewoman from the northern border, has asked for the prince of Dalriada’s help in expelling a howling creature from an old tower on her land—one surrounded by an impenetrable hedge of thorns. Casting a blight over the entire district, and impossible to drive out by ordinary means, it threatens both the safety and the sanity of all who live nearby. With no ready solutions to offer, the prince consults Blackthorn and Grim.

As Blackthorn and Grim begin to put the pieces of this puzzle together, it’s apparent that a powerful adversary is working behind the scenes. Their quest is about to become a life and death struggle—a conflict in which even the closest of friends can find themselves on opposite sides.