Fantasy fiction is rife with characters that can call on a hodgepodge of minor techniques, from rogues who apprenticed as wizards in their youth to priests who were once warriors, often fantasy characters break out of the narrow restrictions of a single class. If a player wishes to create similarly flexible characters they often have little choice but to multiclass, often only 'level dipping' to pick up just enough of a class's iconic abilities to justify a complex background.
Ultimate Combat and Ultimate Magic introduced feats that created alternatives to level dipping: Amateur Gunslinger and the Eldritch Heritage line of feats. These feats give characters enough of the features of another base class to allow players to create characters with concepts that are 'multiclassed' without level dipping, or wrestling with any of the complex questions that come up when taking levels in multiple classes. Inspired by these feats (which have been reproduced here for purposes of including all multiclass feat options in one place), The Genius Guide to Feats of Multiclassing applies this same idea to other base classes, allowing players to build characters that touch on the abilities of the alchemist, barbarian, bard, cavalier, cleric, druid, fighter, inquisitor, magus, monk, oracle, paladin, ranger, rogue, sorcerer, summoner, witch, and wizard without taking on levels from multiple classes.
This means, of course, that this product is not for anyone who dislikes blurring distinctions between classes. That said, the multiclass feats can actually be excellent ways to help sharpen the distinctions between characters, by giving players one more set of options to customize their character choices. Three fighters are going to make a lot of the same choices, but if one has focused on his fiendish heritage (with the eldritch heritage line of feats), one on his duty to a knightly order (with Squire and Champion of the Order) and one on his training as a warrior of the Clan of the Bear (with Berserker, Wodewose and Skin Walker), the characters are going to feel very different even as they take on the same basic tasks of dealing damage to foes. The lines between classes may be blurry, but the characters have grown in distinctiveness as a result.