The worst thing about not attending E3 is missing all those surprise games. The ones that didn't get stage time at the major conferences. By all accounts Middle-earth: Shadow of Mordor was one of those games. Plenty that came back from the show seem to be raving about this game. For some, it was the best game at the show.
The above trailer provides some insight into 'why'.
Middle-earth: Shadow of Mordor appears to be attempting to provide a genuine open world experience with emergent gameplay. Too often that's a buzzword games fail to deliver upon, particularly when it comes to licensed titles, but this appears to be the exception. There seems to be genuine options for players to push in their own unique direction. Colour me intrigued.