Reduce snapper dwell time: It get tedious sometimes when you have to walk past several snappers. I suggest reducing the time snappers spend at the bottom to about 1 second.
Make an option to skip cut scenes: Many (all?) cut scenes could be skipped. If you're going in against a boss you may need several tries and several times through the preceeding cut scene. (Is this what a 'continue' is for? I haven't tried.)
Jump on fire shield pedestal in armoury: When Edgar jumps up to the old shield in the armoury--or comes into contact with any other object that initiates dialog--he stops moving horizontially. This causes him to land at the extreme left edge of the shield column where he's floating in the air. Maybe the easiest thing to do in context of the game physics and gameplay is to have him just walk to the center of the column immediately, or maybe change the geometry of the pedestal.
It's currently not possible to finish the game with only 5 hitpoints: some giant hearts are unavoidable, like the one from the Borer.
Should red book fire balls be quenched in water (maybe melt ice cubes as well?)
Inconsistency among active elements of maps: Snappers, some spiders, horizontal fire spitters, etc. are not destructible, while other objects that can be thought of as having the same role, like flowers, water and slime pillars, and other spiders, are destructible.
Inconsistent menu keys:
It would be nice if the 'Choose slot to load from' submenu, and indeed all menus, could be cancelled by <esc>.
Enchanted weaponry doesn't work on enemies who are charged with the same enchantments (such as with red books and fire and yellow books and lightning):
This is otherwise a really great game.