As I understand it, Jackson added stuff based on the context for Gandalf organizing an expedition against Smaug drawn from the appendices of LOTR and the chapter The Council of Elrond in the Fellowship of the Ring.
It makes sense to do this with the movie version being released as a prequel since the viewers are presumed to know Jackson’s version of LOTR.
It’s still not clear to me there’s enough there for three movies, but two would be easy.
I never read reviews. Most reviewers have an agenda. I’ll be in the cineplex this weekend to see The Hobbitt. BTW as I type this, I have a movie playing on my Kindle Fire, one that was nominated for multiple Oscars but didn’t win even one - True Grit with Jeff Bridges. Free download for Amazon Prime members. Academy members didn’t want to honor a film that honors what’s good about America.