This is really helpful in infinite mode and when you're trying to survive.
To get the 3 power ups for food you will need the 3 books.
The location of the first book would be in the entrance plaza. Right near the entrance on the 2nd floor there is a book store ( sorry I forgot the name) with a health book in it.
Then go to the wonderland plaza and go to sir-book-alot on the 2nd floor and get the other health book.
Then after you defeat the person in crislips store in the north plaza you can enter a room next to it with three survivors and 2 book,s one of the books will increase your food power and another will increase your fist power.
If you get all 3 health books this will get you a triple bonus for your food!