From the introduction:
Just because you have a steady supply of demonic favors at your call, doesn’t mean that life is all easy. The one thing Mephisto can’t do is control people’s minds. Which means if you want that boy you’ve had a crush on to fall for you, you’ll have do it the old fashioned way.
Because in Faust and Friends, the relationships (friends, enemies, lovers, and so on) you have are the most important part. Vast wealth, undying pleasures, and long forgotten wisdom are fun and all, but in the end, its what you make of the people around you that matters.