Adventuring gear is torches, rope, chalk, spikes, flint, tinder, map paper, ink, etc etc. Think of it as Felix's bag - once you pull something out, it's a thing. It's real. Add it to your inventory.
Thus, a bag of books with 5 uses becomes:
- a book of demon tattoos
- a book of snake cult rituals
- a book of elvish chants
- a book of maps of the northern wastes
- a book of recipes using taters