Great game, plenty of good "aha!" moments.
For me, the second room was most difficult. Probably because the clues became much more linear in submitting solutions - solving the first clue helped with the second, etc - whereas in the first room I solved the bottom clues first and everything just fell into place after. Also, I didn't realize the last clue in room 2 (the pictures and grimoire) was all one clue, so I did a lot of second guessing where I shouldn't have.
But in the places I got stuck (that last clue in room 2 was the only place I was really lost for several minutes), once I got the solution I thought "Aha, so that's the clue I was missing!" when I checked the exhibit again. Very well done.