I actually find it much more interesting as to why you felt the need to post this, but I digress.
Sorcery Via definition is based on "evil" spirits, but the word it self first came into use in the 13-1400's, at that time, many things were evil. The word is also acquainted with necromancy (currently used as a cover term which refers to everything from contact with the dead to actually summoning demons) which was labeled evil as people sought answers through spirits of the dead.
I will agree that not all sorcery is necessary "evil" though those (and there are some) that may dig up a person to use the bones for deviation would be labeled "evil" or mentally ill or someone like me would refer to them as something that would be inappropriate to post here.
If your talking about a physical change as in turning into a creature, I would suggest throwing the book away, however some demons are good at projecting hallucinations.