What does great literature need? A plot helps. Great characters. Tension - something to make you turn the page. Excitement, dismay, joy. And at the end, your should be sorry that it is over - and be tempted to start again from the beginning.
Not every great book has all of these virtues. But The Lord of the Rings does - and more.
It would be impossible to improve on the plot, the narrative flow, the brilliant pacing and masterly movement from scene to scene - many of which happen concurrently. And all this from a simple, single premise - destroy that ring!
The characters (of which there are legion) are immediately involving, fully drawn - but the simple old fashioned hooks are there as well. Good guys are likeable, bold, brave, honourable. The bad guys get what they deserve. Some of the Hobbits in particular grow enormously in depth as the book goes on, growing up before your eyes, their personalities re-drawn by the great trials they go through.
Tension, excitement, dismay, joy - you bet. Many parts of all three books are utterly rivetting, veering from edge of the seat, last ditch combat, through great chase scenes, to tense and draining treks through darkness and horror.
And the ending - greatly extended compared to the average work of fiction, and correctly so - is at once uplifting, joyous, beautiful and achingly sad. The sense of greatness and beauty lost, even in victory, is truly remarkable.
And most of all, Tolkien's use of the language he plainly loved is sublime. There are passages that hit extraordinary heights, sometimes lyrical, sometimes moving, horrifying, serene.
I've just re-read this again - perhaps the fourth time now - and it was just as exciting and rewarding as the first time. Put down your prejudices, be bold - it's not "fantasy", it's not "science fiction", it's not for childen - it is one of the very greatest works of English fiction, of any age.
If you have not read this book, turn off your computer and go read it. If you have, go read it again.