This is freaking awesome!  I've browsed literally thousands of asset packs on itch, & this is definitely one of the most unique and interesting ones I've stumbled across. Pixel spellbooks are a rare niche in and of themselves, but what you did with the "open book view" is easily my favorite part (with 11 variants per color, no less)! You really managed to cram an insane amount of detail into a tiny 50x33 pixel space. Also the stacked versions showing the spines with all the different storage/display options is a nice touch.

Honestly the ONLY critique I could even offer: As much as I like the palette you chose, I think the super bright red/blue/green on some of the covers looks just a little jarring? Though idk, whereas the vivid coloration would look a bit out of place in a gritty Diablo-esque fantasy RPG, it would be right at home in a game that was going for a more whimsical aesthetic. Anyway, I fully acknowledge that's just my personal preference, and the fact that you kept those parts to only 2-3 shades would make it very easy to recolor anything I wanted to make more grimdark or whatever lol.

But again, thank you for sharing this, and I'll certainly be keeping an eye out for your future work!