Good game. Challenging indeed. I had to use the guide for the last part. I didn't realize you had to do it in a correct order, misused the books a few times too. I once encountered a bug where some of my items appeared in the inventory after i went to the menu and pressed new game - simply a page refresh gets it good again. I don't dwell the bugs tho. I think you did a good job about making a nice puzzle. The ending could be better, and the overall story could also artistically be combined in a more creative way with the actual puzzle and escape - but I guess your aesthetic goal of the game isn't exactly to be artistic, but to rather make a challenging experience. Good job none the less, I enjoyed it. Music fits too - relaxing. Art-wise it's fine - it might not be the finest quality of art, but it doesn't matter in the case of this game, since the goal of the art is to clarify the items.
Overall a cozy game. 3.5/5!