Let´s face it, if you play this mission just for the mansion, it might not be the right one. The mansion part is ok, but only the surface of the mission. The hidden section is cool and resembles Bonehoard, but it´s intertwined with the TMA parts with a venture of the Mechanists set into it. There are some riddles that are not too hard, the mission manages to motivate the player to solve them even if they are optional.
Luring Mechanists and undead together is also fun and worked for me(with casualties on both sides, the bot blasted up itself while bombing a zombie, hehe). One of the riddles is also a reference to a certain, well, special Thief player...made me smirk.
Architecture is also well designed, object placement good as well, with a good eye for detail(like hidden stuff). So, overall, I would recommend this FM.