Hey, super interesting submission. I really like the children's story book vibe! Some notes:
Cool concept, fun story to follow along with
Enemy types evolved with the story
Solid difficulty levels throughout
Aspects to Work On:
The sound effects, particularly for shooting, get grating after a while because it's the exact same sound. A good practice is to set the sound to pitch slightly up or down randomly each shot, to give the sound more variety.
The ghost characters were a bit jarring. They popped out and immediately damaged you with no warning, might be good to give them a bit of a warmup before they attack.
Some Brainstorms for New Aspects:
Since you needed to reach the end of the page before the level could start, it disconnected the story from the action. It could be interesting to draw the text during the fight, and leave some sort of enemy hint or clue to finish a level in the text, so a player is encouraged to read while fighting, taking advantage of the little amount of text on the screen at any one time.
Some more animations could be a welcome addition. Most characters only had one perspective drawn to them, and only one animation - walking. Some new animations, even if they're a bit crude and only involve a few moving pixels, could go a long way.
All in all, a super interesting submission! Thanks for your feedback on my project as well, good luck in your future developments!