This book updates "The Periphery" (1988) and is, in turn, is updated by "Field Manual: Periphery" (2001).
From the back of the book:
"For centuries, the powers of the Inner Sphere have looked down on their brethren in the Periphery with thinly-veiled disgust. To the "civilized" worlds of humanity, the Periphery is a backwater, not a place where any respectable person would want to live. And many still remember that the nations of the Periphery fought tooth-and-nail against the Star League's attempt to unite all of humanity in a new golden age. Full of hardship, immorality, lawlessness and danger, it is a vast and little-understood region of space.
But that's not the whole story. The Periphery is all of the things that people say about it, but it is also much more. The Taurian Concordat has a better educational system than most Successor States. The citizens of the Magistracy of Canopus enjoy more freedoms than their counterparts in the Inner Sphere. Even the bandit kingdoms are getting into the act, with realms such as the Circinus Federation and the Marian Hegemony making moves towards legitimacy.
Following in the footsteps of ComStar's original Guide to the Periphery, this sourcebook updates our knowledge to the time after the initial Clan invasions, when many changes are taking place and important events are happening out in regions where no one is looking."