Well, I learned a lot of Dutch words from the translation when my father read it to me as a little girl.
I'm currently reading the English version of Lord of the Rings for the very first time, but have not yet stumbled upon words I didn't know or could not figure out from the context. Had I read it before I was a full time Ye Olde English student, this would have been rather different - as Gothmog says, tis not easy reading Tolkien if you're not a native speaker.
When the movies first came out, I learned many words as well. I can remember wield (as in:
'we cannot wield it'), especially. I had no idea what it meant and for years have spelled it as wheeled, to the great amusement of all people more knowledgeable than me.