[Estelyn Telcontar]

I realize that there are many different opinions on this topic; however, for the record, I think it is important to know what Tolkien himself said about the theme of his story. Here are several quotes from his Letters (numbers 186, 203, 208, and 211):

I do not think that even Power or Domination is the real centre of my story. ... The real theme for me is about something much more permanent and difficult: Death and Immortality; the mystery of the love of the world in the hearts of a race 'doomed' to leave and seemingly lose it; the anguish in the hearts of a race 'doomed' not to leave it, until its whole evil-aroused story is complete.

...it is about Death and the desire for deathlessness.

It is only in reading the work myself (with criticisms in mind) that I become aware of the dominance of the theme of Death. (Not that there is any original 'message' in that: most of human art and thought is similarly preoccupied.)

I might say that if the tale is 'about' anything (other than itself), it is not as seems widely supposed about 'power'. Power-seeking is only the motive-power that sets events going, and is relatively unimportant, I think. It is mainly concerned with Death, and Immortality; and the 'escapes': serial longevity, and hoarding memory.