If I remember correctly, there is a hidden ending that is unreachable. One of the storylines is that the aliens are grabbing other life forms to attempt to reach a place that can not be attained by making conscious decisions. Since it is a "choose your own" adventure, you as the reader can not get there either. However, someone had the idea to write a few pages as an ending and put them in the book anyway. Probably to tease kids that would see them as they flipped through the book.
I remember flipping the pages and watching the bottoms for the "turn to" page numbers trying to figure out how to get there. That's when I figured out that it was indeed impossible to arrive at the ideal ending. I still thinks that's a great touch for a kid's book.