I found this to be an entertaining and somewhat unusual addition to the Nancy Drew library of games. As a big fan of the series, I have played my fair share of titles and have become well accustomed to the usual order of gameplay. However, due to the character set up of Castle Malloy, the ending was quite open ended and either incredibly frustrating or strangely enticing---depending on how much you invested in the characters. Placing the mystery in Ireland also made for a fun change of scenery, and I enjoyed the historical myths and legends they worked into the storyline.
Good Points: Great graphics, lots of interesting details to explore. A very large game map. Well developed characters, with intelligent and realistic dialogue as well as surprising emotional depth. A sufficiently creepy castle, and good sound effects. Detailed, and layered storyline involving not only a mystery, but a relationship triangle between three main characters, including two of the suspects.
Bad Points: Some of the tasks in the middle of the story drag. A very complex and time consuming final challenge. Could use more cut scenes to create a more cinematic feel and draw the player in.