Tolkien never described the eye as a
separate physical entity. I'm nearly certain that yellow, wreathed in flame bit comes from
the mirror of
Galadriel scene, in which case it can be interpreted as either a visual metaphor of
Sauron's watching mind, or, what I think, just a close view of his eye so that
Frodo couldn't see anything else. Later in TT Frodo thought he could feel a great eye watching him, which is where the movie got that "pierces stone and flesh" and there was one other thing it pierced, but you know what I mean.
In the book as published in the scene at the Crack of Doom, when Sauron sees Frodo about to destroy
the ring, has something about how the eye--referred to for a short time as "it" fell on him and pierced him and
he (Sauron) was at last aware of how he had been deceived, clearly showing that though the eye was an important part of Sauron, it was still just that--part of his body. The History of Middle-Earth--I believe it was volume IX, but it may have been VIII--had a draft in which Tolkien did in fact use "it" throughout, but subsequently corrected this so that it read "he" everywhere except that first moment when Frodo was perceived, showing that even Tolkien perhaps had come to view the Eye to be iconic of Sauron to point of being
nearly synonymous on some sub-conscious level, but he viewed this as an
error and made a point of fixing it, which goes to show just how misguided Jackson's interpretation is.
This is what is said on the subject in this thread
http://thetolkien.forum/showthread.php?t=15393 about your fav LotR villian, a poll which included PJ as a joke at first, but when he got 25% of the votes consistently for quite some time, ruining everyone else's chances one of the mods changed that spot to
Grima, as he had been forgotten at first.
Very well then, firstly, I voted for Sauron, because he had this way of making you believe he was behind all the other villians even if he wasn't, like in the case of
Shelob. You could never help wondering what passed through that foul mind, what treachery was contemplated there; feeling somehow that he must know your every thought and there could be no escape from him.
Secondly, however, Peter Jackson (who, I note, never appeared in the
books, which is what this section is devoted to) is the real villian because he RUINED the otherwise most perfectly
evil, malicious being ever devised. He took all that wonderful subtlety of a devious mind at work and turned it into a 100,000,000 candle-power "Spotlight of Doom"!