The Last Shield by Cameron Johnston

Look, Cameron Johnston is on my insta-buy list, but he already had me with "a gender-flipped Die Hard set in a mysterious castle". So, The Last Shield pretty much checked all my boxes as I read it. First off, our main character, Briar, is not some young slip of a thing who's going to save the world while making goo-goo eyes at some shadow daddy. She's an older, stubborn-as-heck warrior – a…