See Molly's full review HER-
The world-building aspects of the JCOM RPG are genuinely quite good. A lot of effort went into it, helped along by the fact that there are 11 books and a substantial number of comics to build off of. This results in a few things that lead to a rather open-ended experience for those wishing to create a game.
First of all—and this is quite clever and helps to avoid a common issue in doing a licensed RPG—there are three eras of the world that you’re able to set your adventure in. One is set when the titular character first arrives, before he started making waves, thus allowing you to set your adventures years before he showed up without issue. Another is set during the time when John Carter was established but not quite viewed as the savior of all of Barsoom, and thus allows you to set up your own reputations, or even build a kingdom, without worrying about upsetting him. And the third is set when John Carter rules all of Barsoom, which makes making a name for yourself difficult, but allows for the most interaction with canon heroes if that’s your thing.
And that era system applies to the races you can play as too. There are five races you can play as; your backstory, culture, and how NPCs react to you will all change based on which race and what era. For example, a Green Martian from the early era will come from a very grim and almost Objectivist society, but as time passes they become a much more open and friendly people. The Okar (Yellow Martians) will be very isolationist and arrogant in the early eras, with only a vague idea of what’s happening in the rest of the world outside of their cities, but will be more involved and informed in later ones. Things like that.
It’s honestly a rather good setup. There’s enough to give both the player and the DM (here called the Narrator) plenty of information and a firm foundation (heck, there’s a not insignificant portion of the manual devoted to the history of the planet, and the cultures of the various factions of the races) but allowing for freedom to make your own choices and not be rail-roaded by the canon too much.
[4 of 5 Stars!]