"just a book" or "a descriptive treatise on an imaginary ecosphere " ?

[Guinevere]

Definitely, LotR is more than "just a book" !
I've always loved reading, but when I first "discovered" LotR (at the age of 50!!) it was like a revelation to me. Nothing I had ever read before has so fascinated, thrilled and moved me.
It also inspired an interest for Tolkien and his other works. Before I even started on the Silmarillion, I read "On fairy-stories" (that was a real eye-opener!), "Leaf by Niggle" and Tolkiens biography. Later I also read Tolkiens letters. Every time I come back to read in LotR I appreciate it even more. It appeals to me on many different levels and it is full of wisdom and timeless truth.
I quite agree with Beren87's statement

It's life-altering, life-touching, and life-guiding.

I'm not good at analyzing why that is so, but I guess because it is not just a cleverly written novel but, as Tolkien said in a letter

It is written in my life-blood, such as that is, thick or thin; and I can no other.

I see it as part of the life-work of this exceptional man. Nobody else could write such a book because no other has all his knowledge, his experience and his wisdom.