Read Languages: The means by which directions and the like are read, particularly on treasure maps. It is otherwise like the Read Magic spell above.Naturally, you can toss in graffiti or clues in books. That's not a problem. However, when you compare it to Read Magic, as the description suggests, you notice this:
The spell is of short duration (one or two readings being the usual limit).I decided in a previous post that my ruling on Read Magic would be: 1d6 spell levels per casting, with each command word on a magic item counting as one spell level. But how would this work for Read Languages?
We could take the word "directions" as being the equivalent to "incantations" in Read Magic. But restricting the spell to 1d6 directions seems unusually strict and difficult to manage. Are you honestly going to list every direction given on a treasure map and count the number of directions that can be read?
On the other hand, changing it to 1d6 pages seems too generous. It means an M-U could decipher 3 or 4 maps with one spell. It also means that, for mysterious tomes, you'd have to assign clues or information to individual pages. Too much work!
The compromise: Assume a caster can always decipher one complete map or page with the spell. When they try to read a second map, roll a d6: on 5+, they can completely decipher it and can try another map. If the roll is 4 or less, though, they can decipher most of a map, but the spell fades as they get to the last bit of information. So, you the GM describe all directions or instructions relevant to the goal listed on the map except for the last one. Tell the player that there's one line that couldn't be translated. They can choose to cast a second spell, or go with what they were able to decipher.
For books, I might need some other rules. I want to think about this a while.