LEGO: The Hobbit feels a lot like an extension of
LEGO: The Lord of the Rings, with the added bonus of mechanics added in the
LEGO games that have been released since that older game.
Like LEGO: LotR, The Hobbit gives you a quasi-open world to explore. You are free to move around the land between levels, but you are more or less pushed along a single path to ensure you hit the events in the proper order. As a result, you end up feeling like you are going along the very strict path set down in both the book and films.
Oddly enough, since this game was released with only two of the Hobbit Trilogy films released, LEGO: The Hobbit only covers An Unexpected Journey and The Desolation of Smaug. This feels very out of place for these games. In the past, a LEGO title based on an existing movie franchise tended to wait until there were at least three movies upon which to build. As it is, I can't help but wonder if there will simply be an updated release after the last Hobbit film comes out that contains the entire trilogy. If that's the case, then the smart money seems to be on waiting to get the whole story. This strategy isn't without precedence. LEGO: Indiana Jones was released containing the original trilogy, and then later released with the addition of Kingdom of the Crystal Skull, but again, there were three movies worth of events from which to build. On a similar note, it isn't all that far to expect a larger re-release after the third Hobbit film that contains both LEGO: The Hobbit and LEGO: The Lord of the Rings. After all, TT Games combined their pair of LEGO: Star Wars games with a Complete Saga release.
Enough speculation of what might (and most likely will) happen. The LEGO: The Hobbit that is available now spans the first two films in the trilogy and besides hitting every major point in the films, the game also contains a fairly wide selection of side-quests, as well as a new Loot and Forge mechanic that feels right given that your party consists primarily of dwarves, but more on that later.
As you progress through the story levels, you will not only unlock new characters and Free Play Mode, but you will also unlock hub-world activities that are all designed to help earn you more Mithril and Red Bricks. Like before, Red Bricks let you turn on various cheat codes (like stud multipliers), and Mithril Bricks let you use the forge at Bree in order to create Mithril items to give to other NPCs for more bricks.
One major feature of all LEGO titles from TT Games has been the division of labor across different characters. The fact that some characters can perform tasks that others can't makes for a very natural feeling limiter on exactly what you can do and what you can't. The fact that shiny bricks can't be destroyed unless you have a character with explosives means that you can't do everything all at once, and you will have to keep coming back until you look under every rock. Interestingly enough though, this game gives you a lot of variety right off the bat. After all, you have twelve dwarves in your party and most of them have unique abilities. For instance, only one dwarf can be used to mine ore, while another's big hammer is used to slam large objects around, while another's slingshot can activate targets that the character with a bow and arrow can't. So while you have a lot of capabilities on hand almost immediately, you will still find yourself looking for new characters with specific skill sets in order to actually do everything the game has to offer.