More then likely I'm the idiot and just can't explain things.
It would be a product aimed more towards beginners and could cover the classic campaign ideas. For instance
Evil undead lich raises undead army and players much eventually defeat him. THe book can start with character ideas and suggest ways to cater to the classes. It could remind the DM the power of turning so that clerics in a campiagn with loads of undead can be seen as even more powerful while a rogue that can't sneak attack most of the encounters will be see a bit weaker. It could do that for the different classes and even races. It can have ways to bring the characters together in this type of campaign so they don't have to meet in a bar. It can also suggest adventure ideas liker question for holy weapons, or protecting a caravan of holy water. Perhaps modules that already exist can even be easily slighlty changed to fit the adventure. For instance swap out Blackrazor of White Plume Mountain with an anti undead weapon.