With Gollum, think of an alcoholic's attachment to addiction. Sauron, on the other hand, works for Satan.
If you can, try to catch the replay of this program today at 1pm on EWTN. He explains many of the characters including Gollum and Sorum.
I saw the first half of it the other night, but had to get to bed. I worked this afternoon, so I missed the end.
Great books!