From the publisher's website:
The “fighting man” is the anchor of a huge collection of myth, legend, and fantasy fiction. While it is wizards and dragons that make fantasy… well… fantastic, most often the heroes of those tales are loyal knights, dashing swashbucklers, royal guards, kung fu masters, grim gladiators, and duelists armed with quick wits and quicker blades. The image of the brave warrior is universal, an icon of fantasy adventure from gritty swords-and-sorcery stories to the highest of high fantasy literature. And often these fighting heroes have techniques, styles, tools and talents that go far beyond what can be reasonably represented by Combat Expertise and Weapon Finesse.
Of course, there is a limit to the number of options that can be presented in a single core rulebook, and players quickly crave more flexibility. Fantasy fiction is filled of daring whip-wielders in search of adventure, sage swordsmen who can run across water, prodigious paragons of physical power, and even wizards who use magic to augment their swords more often than they fling fireballs. Some of these characters can be built using the multiclassing rules and prestige classes, but such efforts often feel awkward and the patchwork of prerequisites and additional abilities may blatantly clash with the character’s intended back-story.
The Genius Guide to Martial Archetypes provides material designed to give fighting classes new techniques for running their foes through, or at least flashier things to do while making the effort. It does this through the use of archetype packages—a way to replace some of a base class’s standard abilities with new powers (in this case, powers tied to martial skill). An archetype package can present new kinds of combat options a character may learn (such as the Youxia), allow him to excel in the mastery of a single weapon (such as the Blacksnake), or just give him an extra edge in any fighting situation (such as the Physical Exemplar).