The magus class represents a trope common in fantasy fiction--the warrior-mage able to swing swords and cast spells with equal skill. From classic sword-and-sorcery wielders such as Michael Moorcock's Elric of Melniboné, to the protagonists of more modern fantasy tales such as Garion from David Edding's Belgariad series or Rand al'Thor from Robert Jordan's Wheel of Time series, the warrior-mages are a common archetype often more easily found in fiction than the sage spellcasters with little combat skill. Even Gandalf, perhaps the prototypical adventuring mage, carried the sword Glamdring and knew how to use it to good effect!
Despite this broad popularity, the concept can be difficult to easily implement using only the Pathfinder Roleplaying Game Core Rulebook. While it's possible to multiclass combat-oriented and arcane-oriented classes, and prestige classes such as the eldritch knight are designed to make such combinations fairly effective, the planning and delayed gratification such character builds require are not satisfying to everyone. With the advent of the magus class from Ultimate Magic, players wishing to create a warrior-mage can do so by choosing a single class that combines fair martial ability with good spellcasting ability and a host of class abilities that allow the magus to combine combat and casting in ways other classes can't.
Of course, the traditions of arcane armsmen require much more support than any single book has room to offer, especially since most game supplements have to appeal to a broad range of interests. Ultimate Magic lacks room to present many alternate magus options, and what few it does present focus solely on the narrow concept of a combat spellcaster with a weapon in one hand and only a prepared spell in the other.
To help in that regard, Ultimate Options: New Magus Arcana presents 30 new magus arcana and three sets of alternate abilities designed to work with the new batch of magus arcana options. With this broad set of new material magi can fight with 2-handed weapons, go sword-and-board with a shield, wield two weapons and still cast spells, or even become a spontaneous spellcaster similar to a sorcerer.