The Entertainment Book is a book with discounts. There are books for most states, and some states have more than one region for the book.
What people talk about here is the special super duper rate that HoJo Anaheim gives on certain dates. You can go to any of those threads, or go to hojoanaheim and find the discussion boards there, where there's a whole bunch of questions and answers about the rate and when to get it.
IN order to actually get the rate, you need a book that is valid for your dates (they tend to expire in Nov of each year), for ANY area. If there's a book for your area and you want to use your local discounts, get that one. If there's another area you'll be traveling to another time that year and you want to use the discounts, get that one. If it doesn't matter and it's only for HoJo, get the cheapest one you can. entertainment.com is where to get them (and if you are a part of a rewards site, like mypoints or sunshinerewards etc, go through them for a bit of a rebate).
Then call the 714 number for HoJo in Anaheim, during pacific time business hours, ask for In House Reservations, and see what they have!