although not pop up, it still sits in the same genre, there was a story flip book which allowed you to change the characters, place and what they were doing. The artwork is beautiful and you can make Lando have 3PO's legs on Dagobah watching asteriods etc etc.
It's a really underated book, but brilliantly executed.
If you want to fast forward 30 years, the A Pop-Up Guide to the Galaxy book is amazing too, with some very cleaver graphics and pop ups in there too. A lot of fold outs of ships, plus an awesome Rancor eating people.
Dave.