And yes, it's my first time reading LOTR. My only regret (as you mentioned earlier) is that I didn't read the novels before seeing the films. As I'm reading, I sometimes find it hard to reconcile the images I'm getting from the book with those that I still have in my head form the films. For example, I have to constantly remind myself that Theoden is an old man with long, white hair, and not the youthful, red-haired Bernard Hill from the films. That being said, I think the films are amazing in terms of how much attention was paid to the details and overall atmosphere; I truly feel they do the novel justice.
As for Hithchiker's Guide, I do remember hearing that it was originally a radio drama, and that it was quite good. I love the novel, so it might be worthwhile for me to check out the radio drama in the future.