Darkness Visible and Polychrome are supplements for Stars Without Number by Sine Nomine Publishing (which is a one-man shop run by Kevin Crawford). Stars Without Number is one of the most exciting and interesting science fiction games to come out this decade, and I think both of these supplements expand the possible kinds of games you can use the system for.
Polychrome covers the eponymous world, which is a cyberpunk dystopia. You've no doubt seen and read about cyberpunk dystopias before, and can create your own, but if you're pressed for time, there's one premade for you here. There's a description of the world, NPCs profiles, pre-established conflicts for you to exploit, hooks for why off-world visitors would want to come to Polychrome, all good stuff. Unfortunately, this section doesn't include faction write-ups to use the SWN faction / politics system.
The really exciting parts of the book are the rules additions and game structures in the back half, starting from about page 14 onwards until page 30. You've got rules for "shadowrun" operations, investigations, hacking, new cyberware and other gear, stats for various NPC antagonists and allies, and generators for adventures and NPC resources (one table is called "A Memorable NPC Quirk Is Their..." and another is "What's that Underhab Building?"). At the very back of the book is a PC-suitable handout with the player hacking reference sheet.
This kind of stuff is not unusual, though as always for Stars Without Number the material is both high-quality and extremely gameable. What elevates it above the ordinary bunch of tables, and this is true of most material like this in Stars Without Number books, is the detailed information on structuring play and using the tables as part of that. The information on running investigations is literally one page of text with two columns, and yet it packs more useful advice about how to handle investigations and legwork in cyberpunk games than dozens of similar pages in Dark Heresy. Similarly, the two pages titled "Inside Jobs" dealing with undercover corporate espionage / sabotage almost reads like it was written to cover all the information about these things that Shadowrun 4e left out (for example, how much PCs should be paid) and has a bunch of generic adventure seeds that can be repurposed endlessly, as well as a couple of quick tables to flesh out these seeds. SWN's great strength compared to many other adventure games is its concision and concreteness where other games are prolix and vague, and Polychrome demonstrates that well.
There's also an introductory adventure in Polychrome. I haven't played or run the adventure, so I can't speak to it, but I like that it only takes up six pages instead of say, the thirty-one that the intro adventure in Dark Heresy does.
As fond as I am of Polychrome, I actually consider Darkness Visible the better supplement of the two. If I only had to buy one, it's the one I would buy (fortunately, I didn't have to choose). Darkness Visible is a 97 page supplement about running an espionage campaign. The first chunk of the book deals with the Perimeter agency, which is part of the core Stars Without Number setting. They're an interstellar covert-ops group left over from the previous interstellar human civilisation devoted to preventing technological experimentation from creating existential threats to humanity. I don't use the actual Stars Without Number setting much, so it's of limited gaming value to me, but I did find the section well-written, interesting, and full of gameable ideas. It passed the "Chupp Test", where after reading it, I wanted to play a Perimeter agent.
The bulk of the book is taken up with rules material for running espionage campaigns, and it's a feast of good stuff. There's a subsystem or replacement system for the faction / politics system in stock Stars Without Number that focuses on the resources and actions most relevant to espionage agencies. These rules are meant to by used by PCs to direct the course of the agency they work for, and used properly (as the rules explain), they allow the players to create missions for their characters to go on instead of requiring the referee to come up with them. It's a really well done system, and I encourage other writers to study it as an example of how you can take what initially appears to be a very limited, strictly defined frame for a campaign that appears to provide limited agency (the PCs are operatives given missions by a patron agency) and turn it into a "sandbox" game.
The maltech antagonists are given extensive treatments, including stats, cool new gear, a genetic modifications subsystem and good discussions of how each type of organisation (eugenics cults, doomsday cults, and "godmind" cults focused on unbraked AI) works. There's a lot of work done exploring why and how people might want to tamper with this stuff despite the risks. At the end of this section, there's a version of the Stars Without Number "tags" system for the cults with a random generator.
If you're unfamiliar with the "tags" system, it's a set of randomly generated keywords that are attached to things (mainly planets and factions in the core rules) that have associated entries that suggest friends, enemies, complications, things, and places. These are tied into the adventure generation system in a consistent way so that with a couple of quick rolls you can create entire adventures. The terminology is consistent across books whenever adventure seeds or structures are presented, so you could actually take the tags from the cults in this book, plug the associated subcategories into the adventure seeds in Polychrome or the stock rules, and instantly generate adventures. It's a really subtle, well-done part of the Stars Without Number system that I don't see a lot of people comment on, and it's always surprised me that it hasn't been more influential or studied.
"Tradecraft" is the chapter explaining how to create espionage adventures in detail, and is worth the price of the book on its own. Even if you're not that interested in the Stars Without Number system itself, this section is worth reading through as a very concrete, well done example of how to structure and run espionage / intelligence missions. Once again, it's incredibly concise at 13 pages, with about half of that devoted to specific mission types. After that are rules specific to an espionage game, more background and training packages and some new gear.
What these two books have done IMHO, is turn Stars Without Number into a better system for running Dark Heresy-type games than Dark Heresy itself is. As long-time readers of this blog know, I have a 40K - Stars Without Number conversion, so the idea for me is not a new one (checking my back posts, I just realised I never posted the training packages for warriors and psychics - expect those to go up in the next few days). I think that between Darkness Visible and Polychrome, you now have more rules support for playing a bunch of Throne Agents going around investigating heresy than you do in Dark Heresy itself. If you're currently playing Dark Heresy and finding yourself butting up against what is a very clunky, overly complicated rules system that is mostly available in extremely expensive full-colour hardcover books, it might be worth your time to dole out a much smaller amount of money on Stars Without Number and the two supplements mentioned in this review and switch over. Not only will this be easier on your pocketbook, I suspect you'll actually have a superior play experience.