So... the rules. Pretty much what you're expecting out of d6, with a twist.
You get your normal pile of d6s, but 1 die in the pool is always "Wild". A natural "6" on the Wild dice = advantage, and a natural "1" leads to Complication. This adds a little bit of a wrinkle to the normal d6 dice pools, with an opportunity to insert narrative-style interference (if you wish).
There is also a meta-currency... Hero Points, which provide a simple mechanical benefit (re-roll failed rolls, reduce injury level, etc.). Sure, you can hate meta-currency if you like, but if you blink really hard, it's almost the same as Force Points in the original d6 Star Wars, so there's that.
It really does lean heavily on the original d6 rules. However, the layout seems very fresh and clean. It's a professional job of updating d6 into a modern format, and they didn't go out of their way to reinvent the wheel in terms of what makes d6 useful. It's fast and simple.
Other things they added...
Quirks. I think this is described as GURPS-ish? It's a simple set of descriptors like "Vain" or "Paranoid" or "Impulsive" that can get your character into trouble.
These are balanced out by Remarkable Abilities... again, a set of simple mechanical benefits to certain attributes or skills.
Another addition is "Obligations". These are narrative things that tell you what larger societal ties your character has to the universe. This includes things like Family, the Military, the Regime, and so on. If you fulfill your obligations in the mission, then you get more character advancement awards. If you fail to fulfill your obligations, then there is no penalty... nor is there a penalty if you totally betray your obligations, although you are considered to have switched sides after that point.
While it's fairly minor, I think it does reinforce the Weird World War 1 setting in Carbon Grey in a useful & thoughtful way.
Characters also carry a "Memento", which is like the Signature Item that each Archetype gets in the ALIEN RPG. Again, another character-reinforcing thing that I think is a good design choice.
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The bulk of the Gear and the bulk of the rules have to do with fighting. I think that's natural from the d6 thing? I do have some other d6 rules that I never read, so I'll have to look at those as well... but Carbon Grey's rules have the most detail around fighting, including vehicular combat.
Gear is colorful/flavorful... instead of a "Hold Out Blaster Pistol" (like d6 Star Wars), there are things like "Highborn Defender .25" or "Kreuzotter Emissary’s Sidearm" or "Schattenkorps Whisper Fire Machine Pistol". Again, Gaska & company don't forget what made d6 Star Wars interesting even if the rules weren't that complex around the gear.
Combat is... d6 combat. Throw dice, overcome the target's defense number, then test damage STR against the target STR (or the Frame of a vehicle, for instance). It's good and it works. Initiative is rolled each round, but you can always dump that if you don't like taking up time to do initiative every round.
Vehicle rules include a bit about pursuit, but it's mostly shooting things and blowing up stuff. Of course, instead of X-Wings and TIE Interceptors, you have the "WULF-VOKKER DR910 WARPLANE" and such. (I'll note that the W-V DR910 is not a 3-wing airplane like the Fokker Dr.1 triplane, but I'm not sure what "Dr1" stands for with the esteemed Red Baron's favored warbird... I believe Dr.1 does stand for "Dreidecker", however.)
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Along with the obligatory setting section, which is pretty brief for a licensed game, I think. However, the game does not really care about the story of the comics? This has the benefit of not saddling your characters with what went on somewhere else. You have a whole canvas to work with in the universe of Carbon Grey, which is to your benefit if you don't want to read the comics at all.
There's also a good section on the weird part of the game universe... including a bestiary. The book also has stats for a variety of enemies (from "Cannon Fodder" to "Boss"-types).
Lastly, there are 30+ pages for introductory scenarios ("Episodes"), which is a very good choice for a comic book adaptation like Carbon Grey where people don't have the Avengers baggage and don't know what they ought to do with this material.
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Overall, a good read. You can tell the book was done by a professional. It makes sense as a book. It's well laid out. They've got a lot of amazing artwork to draw upon, and they did so.
This is how you ought to do RPG rulebooks.
(Yes, there's a section on "What is Roleplaying?" ... but there is no "Diversity is the most important thing ever" section. If you search on "Diversity", there's 1 instance in the rulebook... and it has to do with the Archetypes, because a successful party will probably have a diverse set of character archetypes... not race or gender or whatevers. So you have to give them credit for not saying what doesn't need to be said about gender this and racial identity that.)