Just how accepted is magic use in your campaign world? I don't mean is it possible, if you are playing Pathfinder - indeed any fantasy RPG - it's likely that there is at least some magic around; but how does society react to the use of magic? Consider the plot potentials of there being at least somewhere in the campaign world where magic is feared or even forbidden. Then crack open a copy of this book.
First up is a new base class, suitable for use when established religion (perhaps in league with civil authority) has taken against magic use... it's a Mage Hunter, a Paladin retooled for the purpose of stamping out magic wherever it rears its ugly head. An alternate use is also suggested, that mages themselves might use them to deal with rogue magicians who refuse to abide by the rules of whatever body controls magic use, perhaps a powerful college of magic which holds sway over magic use in the area, requiring its graduates or indeed anyone using magic there to abide by its codes of practice. They tend to a professional approach and often do not hold any actual emnity towards those who practice the arcane arts.
Next is a prestige class, the Spellweaver. This individual is an arcanist himself, but enjoys dissecting spells, analysing in great detail how they work... and can disrupt and manipulate the arcane energies that others have brought into existence. The description of how this works is a bit muddled, but it's a potent concept.
Another prestige class follows, the Arcane Luddite. This fellow distains any magical assistance, as a warrior he relies on his own prowess alone. Or at least that's what he says. Many use magic if they must, but only with the ultimate end of ridding the world of its taint.
Next comes a collection of feats to use against arcane magicks. They are quite interesting, and have a range of prerequisites, so carefully planning is necessary to ensure that you can qualify for the ones you fancy. There are also some new class options - for example a Ranger may take 'Spellcaster' as a favoured enemy - and a new weapon enhancement, spell void.
This supplement opens up some quite interesting possibilities. Most campaigns delight in magic use, so you could turn things on their head and run a game where the characters are determined to stamp it out. Or you may choose to equip the NPCs in a particular magic-hating area with these abilities and harry the party when they, all unknowing, trespass...