Nice simple game. The core boxed set alone isn't enough for anything but basic adventures with Kai. The perfect start requires the Core Box and Heroes of Magnamund, which implements a variety of non-Kai careers for the players to select. I recommend it for general play across all ages. And the Core is very reasonably priced.
The artwork is solid and definitely recalls the imagery of the series; the maps definitely do. The material was hands on from Dever until his death, so there's nothing here that is weirdly at odds with expectation. The friends and foes will be familiar to anyone who has played the many books in the series.
If you have read the books as far as book 7, it has everything you need in there. I do not know if any of the expansions go past book 7, but you can literally play through every scene in the game book using the C7 RPG.
This is helped because there are three levels of complexity - the Gamebook style rules, a Slightly more expanded version of the same thing, and a fully fleshed RPG.
Its a fantastic collection of games, and I highly recommend getting the Heroes of MAgamund, for the expansive character creation.
While I'm not a fanatic about the gamebooks, merely someone who enjoyed them and remembers them fondly from back in the day, the RPG material by C7 does the books and the world justice. It's also up to the high benchmark that The One Ring set production wise.