This cracked me up, because I thought someone put it in the SF section to remind the average SF reader that they may want to get off the Ringworld for a little bit, head outside and exercise.

I guess it could have just been some lazy dummy jamming a book into the wrong shelf, but I prefer to think that it's someone with a sense of humor that is unappreciated by his friends, placed by the gods on the shelf where I was shopping, solely for my amusement.