Sorry FFG - really not feeling this one.
I'm sure it will be a beautifully put together book. However, it should have remained as a supplement. Wars are one of the main themes in 40K, and having a big book to help run them in the RPG style would have been perfect. War is an excellent escalation and raising of the stakes for the other games. The acolytes discovering dark secrets leading to wars, succession wars in Rogue Trader, etc. But just a whole new game for the IG seems like a waste.
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Also, personally, I hoped that FFG would have been a little more imaginative if it came to marketing an IG game. I am disappointed that the first thing I see, when I click on a "soldiers" link, is "brotherhood" being advertised. This kind of self-congratulatory, exclusive masturbatory privilege is offensive to a lot of people (including me, if you hadn't guessed). It is a bit of a trend at the moment, to glorify this specific form of machismo.
I would have preferred FFG, whom I respect, to have promoted their new game in a less obtrusive and upsetting way. I'm not a marketing expert, but would have rather have seen something like "Operation: Ground and Pound" or "Over the top, over the top action in the 41st Millennium". Something, anything, less offensive. The worst thing to me is when people do not even realize how this is offensive.
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Still, we will see how the book turns out before purchase.
My main worry for the book, is that it will not cover enough of the 40K universe, and that a lot of stuff will fall to supplements to cover. The table top game has numerous books, one for each force, plus the "specialist" books covering siege warfare, aerial battles, etc. There is no way I can see, that one core book is going to cover all the foes the IG might face, on all the scales, in all the locales. I'm not even sure, with the core rules taking up precious pages, that the book will cover all the IG weapons and tanks.
Even though it is a classic, I kind of hope that the book doesn't cover orks as a central foe. We already have loads of stats for orks in the other FFG books, and the IG rules supplied will serve to cobble together a fearsome Blood Axe Clan, I'm sure. So I'm hoping for something else. If I could choose one, I'd vote Eldar. Very different, and would provide 1-on-1 matches for the IG stuff. E.g. Psykers vs. Farseers, Chimera vs. Falcons, Rough Riders vs. Jet Bikes, etc. This would be a nice way to showcase the rules. If the coverage was not as in depth, I guess two different choices would be better, to focus on the differences between the ways in which the IG must wage war. E.g. Tyrands and Tau.
#1 Fan wish, would be a decent set of simple mortar rules, that was more than a glorified Perception check.
Best wishes to everyone involved in the project!