*sigh*
I feel like a broken record. It's not like this is the first "geek magic" thread to have popped up on this forum, but in the interest of safety I'll repeat myself.
Geek magic is a sub-form of "magic" which is really a far younger tradition commonly known as sideshow. While newer effects have been added to the general roaster, geek magic draws up it's roots from stunts like sword swallowing, fire eating, oil drinking, eating glass, etc. Usually any "effect" that has serious shock, horror, and or potential bodily harm qualifies as geek magic.
Traditionally, geek magic is more stunt than tricks. Magic is a misnomer in the title of this sub-form. Magic tends to imply a trick, gaff, or secret move which by nature suggests a degree of safety that goes along with the effect. Perhaps that alone is where the illusion really is. Most geek effects are "what you see is what you get." Yes, you really swallow a sword, yes you really drive a nail into your skull, and yes you really CAN get hurt doing it.
In recent years such bizarre effects like razor swallowing, control, Russian roulette, saw, etc have made their way onto the scene, and offer a nice alternative to the much older effects typically see around the sideshow.
Since a lot of geek magic's most well known effects ARE dangerous (to a degree) I don't encourage, or advocate the learning of them from anyone else but a private instructor who has had years of experience performing these stunts safely them self. Trust me, a book isn't the best way to learn how to shove bbq skewers through your arms.