Do you know any players who mix up the rules around magic items? Do you maybe want a quick reference as to how many magic item slots a character has? Do you want all of it in one, easy-to-reference place?
Now you have it - How Do I Use Magic Items is exactly what it says on the box: a collection and summation of all the rules around the use of magic items in the Pathfinder Roleplaying Game.
http://www.drivethrurpg.com/product/230965/How-Do-I-Use-Magic-Items