The pink "princess" ones are 9.95 and the gold ones are 11.95 (The gold ones come with a pen that writes in gold ink- note, this ink is hard to see and we had several characters sign over other signatures because they couldn't see it).
These are the two that have spaces for photos. There was also a smaller blue one that just had pages for signatures.
They are available all over the parks and in resort hotel gift shops. You won't have any problem picking them up on the morning of your first day. Disney is smart about positioning them right where you'll find characters. We saw Alice and thought "Oh, we didn't buy a book yet". We turned around and conveniently there was cart full of them for sale right there.