The main benefit of the Entertainment Book when going to
Disneyland is that you can use the card from it (ANY ent book, even the New Zealand book, we've recently learned here!) to get access to a spectacular rate at HoJo (Howard Johnson), if you're going during a time when the rate is offered. You can get a room for as low as $59 base rate during those times.
And it can be any area's valid-at-the-time-of-your-travel Entertainment book.