Most present feeling I have is that this sure was the game made before Little Goody Two Shoes. Which isn't bad per say, but the accomplishments of LGTS shine brighter while the rigidity of this games ends up peaking through.
Pocket Mirror is at it's core an RPG Maker game but with a ton of great presentation and not a lot of aggravating puzzles and death states. The thing is though, that that's about all I can say about it specifically. With it being the predecessor to LGTS, you can easily see how this games direction would go up in scale and and expanding on.
Along with that, since I played these games chronologically, most of the value in the story was seeing how everything had turned out from this game's prequel. It's neat to see which ending was "canon" and how little details lead into this game.
"Neat" is the word I would have to say though overall. It's neat to go back and see the previous works that originated from something you like. Not groundbreaking exactly, but you get to see the DNA of another thing and trace how it developed.