I'm not sure if this game is buggy, or trolling the player, but that whole "lose all the pages when you die" thing basically means the game must be played all the way through without dying. Because if you do die, you have to go all the way back to the beginning to get the pages.
Okay, that could be worse, you're basically playing it through without the bosses. Except...
You need to then wait until you're ready to fight the final boss to get any of the ability upgrades because they don't properly reset when you respawn (so, better beat the final boss on the first try), but it's doable. Except...
The first progress-blocking chicken-wall respawns when you do, and if you respawn past it, you might not be able to destroy it in order to go back and get the early game pages.
I've tried a few times to get the "good" ending, and I'm giving up because it's just unplayable if you're going for 100%.
But other than that (and the somewhat awkward control choice of ZXCD with D being dash - which I find makes for awkward use of jump, attack and dash in combos), a decent mini metroidvania.