Being a really late entrant to the Traveller universe this book is actually my first introduction to what the setting is like. That and I was too late to get a copy of "Behind the Claw" (the conventional setting for Traveller campaigns.)The material devoted to the "Behind the Claw" sector hints at a highly contested section of space divided by three different human empires, plagued by the chaotic Vagrr corsairs as well as anyone devious enough to put together a pirate crew. Throw in a dash of political intrigue and you instantly want to play in that sector!
If "Rim of Fire" suffers anything it's that it isn't "Behind the Claw."
Indeed, the assumptions are quite the contrary. The Sol Sector is decidedly more developed and civilized, lacking the rough hewn frontier feel hinted at in "Behind the Claw." Nearly every system has decent port facilities and there's nothing for the Imperial Interstellar Scout Service to explore. (Buying a Starship should be NO problem what with nearly every starport housing a shipyard!)
What "Rim of Fire" does offer is an epic battle between two dominant races of Humaniti, the displaced Vilani and the descendents of the birth-world of the galaxy, Terra. Though the Confederation is definitely billed as the setting heavies, it's not hard to develop some sympathy, especially since the Imperial side is in some cases equally culpable for Sector unrest.
Also, the sector lies between the worlds of the Aslan and Hiver Empire, both whom provided added tension and potential.
The riddle of the Ancients doesn't seem to have quite the weight that it does in the original setting, and their artifacts and influence seem to be quite sparse, traded instead for worlds struggling with old resentments and a high degree of political intrigue.
And whatever you do, don't turn your back on the Vegans. Encompassed within the sector, this race of previously oppressed aliens has broken the shackles of slavery and technologically surpassed their neighbors. (It's a good thing they're so "friendly.")
By itself, "Rim of Fire" is a rather compelling setting. You're less likely to be attacked outright by pirates or aliens, but don't rule the possibility out! Cutting along the spinward side of the sector is a simmering interstellar border along which the Xth Interstellar War could break at any unsuspecting moment. Indeed the fires from the previous conflict are still smoldering on many worlds.
In essence, "Rim of Fire" offers an intriguing alternative setting for the Traveller universe without sacrificing too many of the conventions one would expect. There is plenty of room in this setting for being heroic or devious. And there are some rather quaint and interesting worlds to visit.