Speaking of which, is the spellbook really that cool? I wouldn't be in favor of selling it, but it seems like using Riltia's mana on her lockdown thing would be more space-efficient.
It's got three spells, including the levitation spell and two we haven't tested yet. Levitation is our best shot at getting our current sidequest done, and also for if we ever want to get that chasm chest. The other two aren't bad either.
FFS mentioned that there was a way to compile spells into a spellbook, IIRC, so that'd be a good way to save inventory space at some point in the future if we can find out how. If it needs an existing book, and doesn't care if it's already a spellbook, we can definitely use that.
All that said, there's no reason we can't put it in storage until we decide we need it again. Doing the sidequest seems perfectly doable right now, though, so we should do that first. After that, I like the grass-pilfering idea and activating the statue with something as possible next moves.
Also, I enjoyed the FF1 reference, FFS! Those shops! I find myself "intrigued" at the "empty" bottles being sold. Seems like a grab bag/lottery option? If so, we should wear our lucky headband to increase the chance of obtaining items/
good items if we should choose to buy one there.
Finally, yeah, that D1 shop
looks expensive, but since it's in Fountain Pence it's actually a lot cheaper than the Stream Ruby shops. If we could only find a currency exchange somewhere we could definitely buy a bunch of stat points up there, assuming inflation doesn't strike again.