That's kupo right. This secret magic shop is hidden behind the waterfall (in the bottom floor) in both the jade pasage and the (what was the name of it?) unknown cave in SoR. The most important tome that you can kupo accquire is Flare, which will cost you 40000. That money can easily be gathered by fighting adamantoise kinda turtles called gilsnapers, or something like that. You what to get Flare because its the best thing to use against the bosses, specially Ultima Weapon. Take your time buying a couple tomes, its worth it!!