Glad you like them!
I' also glad you asked the story question, the menu of FF13-2 has the beginners primer, It basically tells the story of the the first game, chapter by chapter, It's purely text, with some nice music for each segment, I recommend watching HassanAlHajry's walkthrough for anything you missed, I grew bored of the game up to that point, played it to near the end and felt it wasn't fun anymore, FFXIII-2 on the other hand, I still like playing and want more! I believe it is worth the money!
Also Caius's theme plays quite a bit throughout the story!