what do you fine people think the value would be of other language to english books to the general scribe or magi?
Not sure what you're asking, Abe.
First off, "English" doesn't actually exist, nor is it in ~any~ way universal - so let's stick with "Latin" as the default language for Scribes.
Are you asking what other languages might be commonly known? That is, if a Scribe knew Latin (and their native tongue), what would be the next "most common" language?
~IF~ that's your question...
Perhaps Greek, tho' Greece was hardly a "modern" powerhouse, either culturally or economically/politically, and so only ancient (and thus relatively obscure) texts were in Greek. Not that the Eastern Roman Empire wasn't powerful, they just didn't flex their power much beyond their borders and immediate neighbors (Eastern Italian coast.)
But each language we associate today with a single country was still fractured into multiple dialects (if not outright distinct languages!) at this time. "English" was Welsh, Anglo-Norman French, some Norse languages and any number of Anglo-Saxon sub-dialects. "French" was broken into more than about a half-dozen sub-dialects - Frankish, Norman, and Langue-doc being the most dominant, plus Parisian and other city dialects. "Swiss" was actually at the time almost a trade-pigeon of the bordering versions of French, German and Italian, and in fact each valley had their own dialect, not particularly helpful in the next valley. "Italian" was widely known in one form or another, if only because it was so close to Latin (many later/modern scholars learned Italian almost by accident.) But, again, at this time "Italian" had no single language, and each city had its own distinct dialect - Roman, Venetian, Sicilian, Neapolitan, and so forth.
It wasn't until a combination of a strong centralizing and unifying goverment (which few countries had at this time) and the printing press (likewise, ahem) did a single semi-stable* version of any language develop. And until that happened, few "localized" languages were very useful, except to neighboring regions, and then mostly only to those who traveled between there.
(* Read Shakespeare in the original, and realize that was only, and after printing and dictionaries (both ca 1600) had begun to "stabilize" the language at that point. And that English has not been the most changed.)
So... if it's not Latin, and it's not "the local", or a strong neighbor, it's a complete crapshot as to who knows it, and odds are "no one around here". Which is exactly why Latin was so important for so long.
But a text written in Latin that explains the "Local" language (or tries to), or vice versa, or even a "Local (to) Neighboring Language" book would be handy, yes.
Among scholars of 13th century Europe, Greek may very well be 2nd biggest language, lots of older texts only survived in their Greek translation after all, but its hard to say. Greek did survive as a "language of the learned" up until nearly the last century though so its almost certainly in the "top 5".
Also big ones, French for sure, maybe German, maybe Polish. It was very common that anyone who traveled or interacted with people from many regions "simply" learned another language.
Latin was the "biggie" though.
Yeah, definetly useful. Also, the written versions of languages tend(ed) to be more easily read by those speaking different dialects so a "dictionary" in French might be able to cover more than one dialect even if the spoken dialects are unintelligable between each other.
Similar to how here, its common with text in both Swedish, Norwegian and Danish on labels and stuff, and read, the texts are often easy to see what words are the same(as they often ARE the same) but if you hear the same spoken "by a native", its suddenly a whole lot more difficult.