If you pick up this book, I highly recommend another book written by the same author - Michael Ende - called Momo.
The fantasy parts of the NES sometimes feel like allegory but mostly feel like folly. But Momo is ostensibly an allegory from the beginning. It also feels like waking up your inner child.
The parts of the NES that were not adapted into the films are absolutely whimsical and amazing. It's a true wonder why some details were used in the film and not others. It's a lot of fun!