The Game Steward
The biggest difference is that the Second Edition now comes with the Book of Encounters (which itself has been edited and corrected from the first edition). It replaces the deck of encounters, which is still available from the 8th Summit website.
From the Second Edition Kickstarter Page:
1ST EDITION BUYERS: Gameplay in this new edition has not changed. The new edition provides a newly edited book. The encounters are the same, however, and no additions were made. You have no reason to buy a new copy of this game, unless you want the new box and edited cards inside, but you may want to buy the new promotional items and the newly edited book. On a future date, you may order only the book if you wish, or may order a combination of new and old promotions. This will be made available later on our website.