Im not a fan of hidden object games, and its a disappointment that you can no longer search for adventure games in the App Store without getting a lot of hidden object games and games with adventure themes. Blackthorn Castle is a well-made old school classic point and click adventure game that Id recommend to fans of The Room and the Myst games, as well as the variety of escape-the-area puzzles that have been around for the past decade or so. Its attractively done, and for the most part, its interface just "works."
My only quibble is that the maze is difficult without directions turned on, because its otherwise hard to tell whether youre coming or going.
If you like this kind of game and you happen to be looking when this one isnt free, dont worry: its worth the full price.