I'm surprised at the number of reviewers who found this game disappointing.  I found it to be a challenging expansion pack that significantly raises the difficulty level over that of the original.  No, Tales of the Sword Coast doesn't extend the story line of BG, and, no, the story line doesn't even FIT comfortably within the original BG plot.  And yes, Tales IS basically  an add-on that simply allows your characters to increase their experience points and find new items in the process.