Just bought the book. Good stuff:
You could use this as an opportunity to take some stats on the film since you'll be watching it so many times. Like which characters interact the most, or how many scenes the Delorean is in, or whatever.
You could also do some research on the making of the film and see if you can spot any easter eggs. I'm currently reading this book, and I know if I ever watch the trilogy again, there will be things that I'll be looking out for.