Used Leap Pad Learning System includes backpack and four books with cartridges.  Tested all books and cartridges, and they all work.  The backpack has some staining (see photo).  Runs on 4 AA batteries (not included).
Books and cartridges include:
Letters and Letter Sounds
Math - Tad Goes Shopping
Alphabet Adventures
Disney Princess Stories

I purchased this used to give to my nephew's son, only to find out his grandmother has put a new one on lay-away for Christmas (bad Grandma!!).

I'm happy to answer any questions, and thanks for looking.