Last year was the first year I purchased an Entertainment Book for our family. Let me just say it paid for it's self in about 2 weeks. I am planning on getting one for this year now as well. My guess is that we will saving even more by using it this year as we will be doing a lot more locally to save on gas.
If you order now through this link you can get a very sweet deal. You can get in on the 2011 Entertainment book at 75% off and get a $25 Restaurant gift card for free. The Entertainment books for each area vary in price so you will want to check on the price in your area. For details on the offer check this out.
The main stipulation seems to be that you have to reserve a copy of next years Entertainment Book.