Read Magic: The means by which the incantations on an item or scroll are read. Without such a spell or similar device magic is unintelligible to even a Magic-User. The spell is of short duration (one or two readings being the usual limit).There's no range stated for either, but then it's possible to consider these as affecting the caster only. The maximum distance from the caster to the text being read depends on the lighting and text legibility, not the spell. Of course, there's no specification in the original spells that they cannot be cast on another person, so that range could be considered 10 feet, based on my tentative suggestion of a 10 feet/spell level default.
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.
The duration again is merely specified as "short". One or two readings, but that's only "the usual limit", implying some leeway. We might instead want to consider the duration as permanent, but with a limited number of targets; in other words, you can read one scroll or one map, but you will always be able to read that scroll or map from then on, Longer texts take longer to read, which would explain the open-ended duration, but an entire book might not be readable in one sitting.
I think a good ruling on this would be to allow someone to skim through a "chapter" of a mundane book for a maximum of ten minutes, as long as the reader isn't interrupted. Roll 1d6 to determine how many chapters are in a short book, more dice for more massive volumes. Skimming gives the general gist of what the book contains, plus it makes that particular text permanently readable, for research purposes. Trying to find specific information later will require more time.
The Read Magic spell appears to have originally been a "gatekeeper", blocking immediate access to something; in this case, magic scrolls or activation inscriptions on magic items. You can decipher magical inscriptions later, at great expense over several weeks, or you can cast Read Magic now -- but that means devoting a spell slot you might prefer to use for something like Sleep. the intention, then, was that scrolls found in the dungeon would normally not be usable until much later, with Read Magic allowing you to bypass that rule.
Similarly, Read Languages blocks the immediate use of maps. This lets a GM skip preparing a bunch of mapped locations beforehand. The total number of available 1st level spell slots for all magic-user characters is the maximum number of times the players could case Read Magic for that adventure, so that's the maximum number of map locations the GM needs for a given session. You don't even need to draw up actual map handouts beforehand; you could just do a bunch of sketch maps with no notations and say "There's also writing on the map you can't read." When a player casts Read Languages (or a thief successfully deciphers a map,) ask for the map back and write down the directions and notations.
One of the implications I draw from the linking of these two spells is that you could apply the magic research rules to deciphering unknown languages as well. Treat most languages as equivalent to a 1st level spell and assess the usual costs (100 gp for every 1% chance of success.) An exceptionally difficult or lost language might be treated as 2nd level, and other languages could be linked to spells associated with the creature that writes or speaks that language: monstrous (non-humanoid) creatures can only be charmed with Charm Monster, a 4th level spell, so their languages could be rated as 4th level, while languages from other planes would be considered 5th level (like the Contact Other Planes spell.) This is only for determining mundane language research costs; it does not affect the Read Languages spell, nor are these other spells required to decipher hard/rare languages.