A great book that not only expands on existing options to have practices influence game mechanics but also offers a more nuanced take on evil practices beyond 'Kill people for infernal investments.' I personally did not like how high power characters had to make a permanent choice between versatility or specialization but the idea is one I would love to include in my games after a bit of homebrewing to make it so that the choices merely cause an increase in experience cost rather than permanently banning sphere advancement.