This was my “Eight Dollar” souvenir. To answer your questions:
What is it? You may need a passport for Canada and Mexico, but you don’t need one for National Parks (yet). This is a handy little book that lists all of the parks, monuments, etc. of the National Parks Service, by area. It also has a full US map, and spots for cancellation stamps.
Since we got an annual pass, and had many NPS stops on this trip (most of the big stops!), we thought this would be a great resource. I liked the spots for cancellation stamps. Each park/monument has at least one spot with a unique, dated rubber stamp to mark your book. It’s like a passport stamp. There is an element to scavenger hunt, since some parks have several different stamps and designs.
Why is it “eight dollar” instead of eight dollar? While the book only cost $7.95 and the stamping is free and we had the park pass to get in, I also liked getting regional and park specific “featured stamps”, which are like stickers. I probably spent about $25, total, but I’m still calling it an Eight Dollar souvenir.