I'm looking for a phrase that will allow me to say things like this:
Having learned English allowed me to read more books [in their original language].
You’re nearly there already: in the original is probably the most usual wording for this. Or to be more specific you can say in the original English, or whatever other language is in question.
I found this a bit irritating: if my French is insufficient to allow me to read Proust in the original, why should the editors assume that I can read Racine? — Stephen Fall, www.readingproust.com