Well after playing the Lord of the Rings Online for a couple of weeks, I've been fairly impressed with the level of Tolkien inspired incidents in the game that weren't in the movies. For instance one of your early quests is to swing by Frodo's house in Crickhollow to help Fredegar "Fatty" Bolger who is staying in the house hoping to delay the servants of the enemy, aka the ring wraiths. This is a subplot from the book that isn't in the Peter Jackson film of the Fellowship of the Ring.
Later you encounter the treacherous Bill Ferney, who is in league with the ruffians of the mysterious Sharkey. Again, threads from the books. There are also a lot of ruins and such that are mentioned in the appendices of LotR which you visit as parts of quests. You have to go into the Old Forest near Buckland and visit Tom Bombadil and his wife Goldberry. Tom is pretty much as you'd expect, dancing around and hard to pin down to ask questions. He even speaks in rhyme. And his boots are yellow.
Basically you're running around on the fringes of the book/movies plot, having adventures in between those of the main characters from LotR. The only main character I've interacted with so far is Strider (Aragorn) who is waiting for the hobbits at the Prancing Pony in Bree, but has time to send me on a couple of missions.
I've only begun to travel in the game but I've seen quite a bit of stuff pulled from the books. Good to see that the game developers have done their research. You don't have to have read The Lord of the Rings to play the game, but if you have, you'll pick up a lot of extra nuances and references.