I would associate it with the books. I like the sound and the look of it, but not the character.
It has been used as a name in Wales before the book came out in 1954, but only a tiny number of times - according to birth records, there have been a grand total of five people given the name
Arwen in Wales between 1837 and 1954, and I think they were probably variants of / typos for Arwyn (boy's name meaning 'very fair') or
Arwel (meaning unknown).
There's always
Anwen or Awen, if you want something similar with no Tolkien associations.