This latest addition to Lego gaming probably has the best audio and music of the franchise to date as it's taken straight from the films. The game covers all three films.
Story mode covers about 30% of the game and on a quick play through (because w/end telly was rubbish) Fellowship of the Ring took 7 hr, Two Towers and Return of the King 5 hr each. I've read that they are each broken into 6 chapters but the game is captivating and played the whole thing in 3 sittings. Although 17hrs for the story seems short there are lots of challenges, collectables and side quests still to do and I guess these will make up the rest of game. Because of the high production values I don't feel short changed - it's just something to be aware of prior to purchase.
The story mode chapters are linear and typical of the previous games but are seamlessly linked with the unlocking open world of Middle-earth which has it's own puzzles and challenges.
Each character has a different skill set i.e. Sam (grows plants, digs, lights fires), Merry (fishing), Legolas (archery) and Gimli (smashes stone) - so most of the puzzles involve choosing the right character for each task.
The prologue with Isildur and Sauran feels a bit dark and plunges the player straight into combat but once the game starts "proper" with Frodo at Hobbiton it immediately recover's the lightness and fun that typify these games. As you play through the story the levels of Middle-earth open up but you can back track at any stage. There isn't a mission hub (other than the Map's "Fast Travel") and when the main story is completed you can literally walk from Hobbiton to the Black Gate of Mordor.
Open world Middle-earth areas such as Hobbiton, Bree, Weathertop, Rivendell, etc are free roaming and require a little exploration to find challenges (horse riding time trial, archery, whack a mole), items (ie keys and cranks by fishing or digging, Mithrial Blocks by 3D platforms/jumps), quests (find an item in a particular place), etc.
Middle-earth is perfectly miniaturised and although no sooner do you leave Helm's Deep than turn a corner and reach Isengard, because all the levels are connected, the world feels bigger and you'll use the Map's "Fast Travel" to get from one end of the world to the other or to get to Bree to forge that new item.
IMHO some of the video game (fighting/shooting) elements of the story chapters might be challenging for younger players so would be best played with an adult/older sibling on hand for the first play through. Then they can then enjoy exploring the open world.
Once unlocked a chapter can be replayed in
1. Story mode with a limited character and equipment set to get missed items or a high score
2. Freeplay with any unlocked character and/or equipment to get to those impossible to reach places.
or the open world explored for challenges and quests.
The usual Lego features are present (but not via a hub shop). New unlocked characters are purchased when met in the open world. Custom characters (Max 10) are created at Bag End in Hobbiton. Red blocks (Bonuses and Cheats) are purchased after completing quests. If you have found the design and have enough Mithrial blocks new items are forged at the Smithy in Bree adding new skills to the Treasure Trove i.e. so anyone can fish.
It is these open world Middle-earth challenges, quests, etc that extend the longevity of the game.
Drop in and play 2p multiplayer is available throughout and players are not limited to particular areas ie. In open world Middle-earth one player can be solving puzzles at Hobbiton and the other at the Black Gate.
All in all if you enjoy the lego series and/or LOTR you'll enjoy this so it's recommended.