So, I managed to get a copy of the latest Warhammer 40k Roleplay book, Black Crusade. And so far, I kind love it.
Unlike the other games in the WH40kRP line, you are not servants of the Imperium of Man - instead, you are renegades, worshippers of the Ruinous Powers, determined to eke out a living in The Screaming Vortex - a huge Warp Storm, filled with worlds untouched by the lies of the Imperium for centuries (or in some cases, millenia). If they manage to achieve infamy, gain the loyalty of cities, worlds, perhaps even whole solar systems, they might just be able to pull off what many have tried, and most have failed - a Black Crusade, a torrent of Chaos to throw off the oppressive shackles under which humankind toils.
In other words, you play the bad guys - and apparently, have a lot of fun doing it.
The first thing that strikes me as I read it is the tone - the entire book is written from the point of view that the Imperium is objectively wrong, and paints the Heretics in the best light it can - misunderstood visionaries, freedom fighters, etc. It's pretty cool - they even manage to salvage a lot of reasonable-sounding quotes from some of the biggest villains in the setting! But, try as they might, it is pretty obvious that what you are doing is, well, evil - misguided evil, in some cases, but generally evil. It's a very cool way to show that, while they might have best intentions at heart, Chaos is not simply a tool to use to further your own agenda - it becomes your agenda in next to no time. It's also interesting to note that, while the other books are very forgiving of some of the Imperium's more extremist behaviours, Black Crusade lays them all out, and talks more about why they're so strict.
Character creation is a little different from previous games - whereas before you had a set Career Path, with its own place within society and its own rules and expectations, BC has an almost completely freeform advancement system. You start with an Archetype - like Psyker, Renegade (a freedom fighter, with the emphasis on "Fighter"), Apostate (the charming herald of the Ruinous Powers), providing starting skills and Talents, and after that, you can pick and choose what Talents and Skills you wish to take. However, some are linked to certain Chaos Gods - taking talents that improve your fighting skill, for example, will lead you down the path of Khorne. This, in turn, makes it easier to buy other Khorne-related talents and skills - but makes ones from the opposing Gods (Tzeench and Nurgle is a little bump, but Slannesh, being directly opposed, costs a lot more). The more talents you buy, the more you follow a certain path - and the more likely you are to attract the attention and Gifts (however unwanted) of your patron. It helps to secure a "path", but doesn't lock you in - you can still buy those opposing skills, just at a much higher XP cost. It's a nifty little system, and no mistake. (You could just stay Unaligned, and reap the benefits of all the paths - but it'll be much harder to balance, and it'll cost you in the long run...)
Another interesting factor is your choice of "Race" - whether Human or Chaos Space Marine. I was awfully unsure about mixing both these character types within the same range of XP, and the system used to do so is a little bit iffy - CSMs start with free Traits (like all their Astartes Implants, and the ability to use fuckhuge weapons), whereas Humans start with a lot more Skills and other random Talents. This should, in theory, balance out, but in practice it seems to mean Humans are more versatile and useful, while CSMs are pretty much just combat monsters. This is entirely keeping with the fluff of course, (Space Marines are made for battle, and for a human to survive in the Screaming Vortex, they have to be pretty hardcore) but there you go. It seems most people recommend running games with either Humans or CSMs, but I guess having one CSM in an all-Human group (or vice-versa) would help keep things a little bit more balanced.
As with most of the books, the armoury is pretty swish - a lot of very flavourful weapons, perfect for everyone from powerful Chaos Space Marine Warbands, down to the least-equipped cultist. Also, each has its own little bits of cool description and plot hooks within the description, so GMs can really think about why their enemies are armed as they are. Personal favourite - the Chain Halberd. Why? It's dumb as fuck, but also strangely well thought out (it's for fighting in the tight corridors of Hives, where reach is pretty important!)
There's a lot of notes on how to draw characters from the other gamelines into the game, or from here into the others - which leads to a lot of potential awesomeness (so, any other gameline, the characters might fall to Chaos, but in particular, the Dark Heresy stuff is great for small-scale cat-and-mouse cultist games, and the idea of crossing Rogue Trader into the mix really helps set the epic scale at which one should be running a game where the players pull of a Black Crusade). This info also helps GMs to use the opponents and fluff here to make some very memorable encounters and villains.
The book also contains a lot of re-jiggered rules from the older games - most are for the best, to cut down on some of the more ridiculous excesses of previous games (Unnatural Characteristics, for one, replacing the multiplication with a static bonus - less bookkeeping, less hassle all round), and some which help to balance out other problems. They're pretty well done, and it's something that is also pretty easy to port back into the older games.
It also marks the first proper appearance of both Dark Eldar and Necrons into the 40kRP line - puzzlingly, however, they stuck with the old "Terminators in Space" feel of the old Necrons, with only the briefest mention of the tendencies for diplomacy and individual thought shown in the brand new codex. Whether this is simply due to bad timing, or contractual stuff, I don't know - but if I ever use Necrons, they're gonna follow the "Opposed Feudal Warlords Who Happen To Be Immortal Skeleton Robots in Space" angle.
All in all, it's a pretty good book. Even if you can't stomach the idea of running a campaign with it (and I'll admit, I have my doubts that it won't turn into some kind of gross-out, rape everything in sight then try and murder and sacrifice it to my Heathen God kinda thing), it's a great resource for building antagonists, with new Psychic Powers, Techniques, enemies (the Daemon Prince suggested in the book is awesome, though a couple of decently-equipped Deathwatch Marines could probably skullfuck it in seconds), equipment, and even motivations and possibilities - and don't forget those rules updates. They're delicious.
Well worth a look, at least.