Thirteen (Horror book)

I've stumbled across this book and everybody is saying that the first story is the scariest thing they have ever read, I'm a lil' short on cash right now so I don't plan on getting it any time soon. To anyone that has read it, can someone explain to me what happened? I heard that you're supposed to interact and follow instructions, alot of people apparently bailed on the final step due to getting too creeped out.

And to those that don't know what I'm talking about, here is the link to it's website:

http://www.thirteenhorror.com/

Hmm I might have to get that just to see what all the fuss is about.