Let me start by saying that, while not without its flaws, Deep Carbon Observatory might just be my favorite "DIY," self-published adventure module. This is a unique creation that is superior than most from conception through execution. Nontheless, while my enthusiasm for the material tempts me to give it a perfect rating, I'm going to hold back in the hopes of providing a review that would be useful to any potential buyer that would actually intend to DM the adventure as written.
The compelling concept, the imaginative vision, and Stuart's comendable writing are what really set DCO apart from the crowd. DCO was clearly a labor of love for the author; the excellent work on his falsemachine blog is a testament to his obsession with fleshing out and even re-invisioning the Underdark. Though I have no doubt other, perhaps even more ambitious works in this vein will follow from Stuart, DCO might be seen as something of a culmination of his public work at this point in time. Many of the ideas first presented on his blog regarding Underdark denizens make appearances in DCO, and the wierd, gloomy atmosphere set by his evocative blog posts pervades the module as well.
In fact, the consistent mood of bleak dread and otherwordly mystery is perhaps the strongest feature of the product. The reader can't help but be caught up in wonder of the scenario; reading along, I felt as if I were the adventurer myself, eagerly uncovering one secret after another (though, of course, without the constant fear of a horrible, lonely death!). This is largely due to Stuart's superior writing ability; this is an author that truly has a way with words, infusing many of his descriptions with not just cleverness, but with a poetic language that I just do not find in most RPG adventure writing I've read. While this level of writing was not consistent throughout the entire module, the times where it did hit those high notes provided me with a great deal of inspiration and a real desire to incorporate this into my campaign (or even use as the basis for a new one). Equally rare is Stuart's ability to create of sense doom and awe without descending into pointless gore, overwrought "wierdness," or ham-handed attempts to shock the reader for sake of being "edgy." He also manages to creatre scenarios that put the PCs in serious danger, yet I never got the sense that he was going for some kind of PC body count or trying to unreasonably screw the players.
Without giving away much of the plot (in case you're the rare player that is module-shopping for a DM or you just enjoy an unspoiled readthrough), I'll say that the full adventure offers a great deal of variety. An interesting chart of possible events, based on PC decisions, provides hooks and lead to short- and long-term consequences. Following this jump-off point is an overland journey that provides several unique encounters with opportunities for treasure, confrontation, and the unveiling of mysteries. After this, a short dungeon and an exotic locale precede the final delve into the Observatory itself, a memorable location that I found excellently envisioned from Stuart's borrowing of the ominous name to his design of a complex that players will both dread but love to explore. And trust me, there is plently here to both dread and marvel at, and all I will say is that your players are not likely to forget their excursion into this strange and silent domain. During all this, the machinations of an NPC party, whether known to the PCs or not, provide a sense of urgency and even the potential for dire ramifications for a campaign setting.
The artwork accompanying will likely meet with a divided audience. I found Scrap Princesses' unique style very appropriate for the material. My reaction to individual pieces was mixed; some drawing were evocative and helped me envision the subject matter (including a few amazing, stand-out illustrations), while others fell flat and seemed to do little for the module other than fill space.
Moving beyond the more aesthetic qualities, the mechanical aspects of the module are also a mixed bag. I appreciate that this is a module that expects the DM to do some legwork on everything from maps to monsters to background. I write much of my own adventure material, hate stat blocks, and am fine with filling in the blanks as suits my campaign, but I understand that not all buyers will fill this way, especially given a $10 price tag. I mention this in the interest of fairness to such buyers; just be advised this is not a fully "ready-to-run" product, though it does come close depending on your specific needs. There are other incomplete aspects I'm less inclined to hand-wave away. The "rough sketch" nature of the maps worked well for a couple but left me hanging on others, trying to piece together rhyme-or-reason with the aid of the room descriptions. While I realize this too was likely intentional, I would say, for me, that it is often easier to create maps from scratch than it is to reconstruct one from an incomplete or unclear description.
Another source of occasional frustration as the scattered layout of the background details and explanatory material for various monsters, rooms, set-pieces, etc. This is a common complaint I have with many DIY adventure modules I've read; the module unfolds like a mystery to the reader, revealing a detail at a time, usually requiring re-reads and deciphering to finally achieve some kind of an understanding of the modules secrets. While this makes for an engaging and fun read on your first time through, it can make for a hassle if one actually DMs the adventure. I'm not sure if these techniques are employed to avoid the dreaded "front-loading" of background material or just serve to highlight the cleverness of the author by inspiring numerous "hmmmm.....AHA!" moments, but in terms of practical functionality, I find this style only makes the DMs task harder.
Ultimately, this is a module that many DMs will find an irresistable addition to their table, and many others will enjoy a great read and a source of inspiration. Those not used to the quirks of DIY modules may be turned off, but I think the concept and writing here are strong enough to make this a product that will appeal to many RPG camps, regardless of edition. CongratulatiThis is a job well done; Stuart's vision of the Underdark is the one I want in my campaign.