This is the second book in the Iron Locket series. It may stand alone, but I think you really need to read book 1 first.
A fantasy story with King Arthur, Lancelot and Guinevere. As the Four Queens try to reign and fight against evil, the story unfolds. Guinevere, Arthur and Lancelot may have been the first love triangle, but the new love triangle is Guinevere, Arthur and Aoife. At least Guinevere tries to make it a love triangle. Arthur has other ideas.
This is a well written book. I recommend reading the first in the series though before reading this one. And I do recommend reading this one. I didn’t enjoy it quite as much as #1 but it is a nice continuation of the story.