After taking a hit of Soy Sauce, John and David start to see things, scary things, horrible things. Next thing they know, they're trying to save the world. 
 John Dies is rather haphazard. It's very funny (you know, penis and poop jokes funny) and reasonably scary (I had one night where I briefly considered leaving the hall light on), but it's all over the place. 
 It was a fun read, and the titular John was absolutely hilarious (gotta love the puns), but it just never seemed to go anywhere. the final portion of the book, where the author tries to give an explanation for all the weird stuff, feels very forced. It's rather clear that he hadn't really thought through where the story was going until he got there, and no amount of world-destroying dog diarrhea can cover that up. 
 It's brain candy - no nutrition, but enjoyable enough in moderation.