Fixes enjoyability on 0 charge books and the cannibal cookbook.

Due to a little bracket slip-up, books with 0 charges were giving full enjoyability when they're meant to only give half of it.
As well, To Serve Man was correctly giving positive enjoyment to players with cannibal, sociopath or sapiovore traits, however after more than 3 consecutive uses the morale bonus turned negative (sudden shift from +75 morale to -75!). Admittedly my fix might not be too elegant but it's working as intended now.