I usually take a small wire-bound photo album with cut-to-fit sheets of scrapbook paper that my daughter uses for autographs. I like this because it's a lot less expensive, and I can then transfer the sheets to another photo album with a picture with the character, or put them straight into a scrapbook.
However, on our last trip I forgot the autograph book so I had to buy one in the Magic Kingdom right before Storytime with Belle. The books they sell there are $6.00 - the same one on the site mentioned was listed for $12.95, and I assume that's without shipping. Personally, I'd rather just wait and pick the same book up for half the price at WDW. They have them in all the resort gift shops if you want to make sure you pick it up before you get to the parks. Otherwise, you can get one from the first store/cart you see after passing through the gates of any of the parks.
I will admit, I've just spent the last week scouring local craft stores for autograph books for our upcoming August trip. It'll be a multi-family thing with one family who has never been before. I was hoping to find relatively inexpensive unlined memo books or something for all of the kids (6 in total) but couldn't find *anything* useful for that purpose. So I'll probably take both of my DD's autograph books (Disney and homemade) and let the other families decide if they want to get into the autograph game when they get there.
Mur!