This is a simple canvassing question, Jeff-style: Given that I started re-reading Delta Green tonight, and was again swept away by the honeyed words of Dennis Detwiller and company, what other rpg texts would one recommend to somebody wishing to read good books?
The same question might be expressed by stating that I'm interested in good settings or campaign books, but that's not quite enough; there certainly are settings that are good (as objectively as one can state these things, anyway) without being presented in a compelling literary form. Thinking of a good example, I'll suggest Exalted: I think it's a compelling setting, and arguably there are source books more and less dense in interesting setting prose, but ultimately the Exalted books I've read have been merely mediocre as reading experiences. This probably has to do with an excessive amount of nitpicky mechanical crunch, the sheer length of the supplement treadmill (which forces them to parcel out the material), plus the flatness of the presentation (too much gazetteer, not enough campaign framework, which is of course arguably a virtue for actual gaming use), or something like that.
I'll list a couple of examples of what I personally consider to be rpg texts with high literary quality. You probably have your own ways of evaluating an aesthetic question like this, but my benchmark is simply whether the book stands up as a relevant work when stacked next to other literature in its genre. In other words, it needs to be good enough to read even if you don't actually plan to play it.
Glorantha materials occasionally surpass my benchmark. The King of Sartar setting history slash fantasy novel ranks particularly high to my mind, it's a delightful and relevant read for anybody interested in good fantasy literature (of a particular Tolkienist sort, perhaps, but still). Actual setting sourcebooks are also regular good reads; the less mechanics the better, generally speaking.
The aforementioned Delta Green essentially builds its line profile on this stuff: the books are nothing but exquisitely detailed conspiracy horror scenarios of the highest caliber. The rpg sourcebook format (consisting of setting exposition and adventure scenarios) actually works pretty well for this sort of literary material compared to your typical novel structure with its plots and explicitly arranged drama and such. The information density alone is to be commended, not to speak of the degree of realistic detail; such features make for something that far surpasses say X-Files or Atrocity Archives or other works of the genre in quality.
Pendragon, and particularly the Great Pendragon Campaign, are an interesting and rewarding read for anybody interested in historical, mythical fantasy. Few Arthurian fantasies are as detailed, self-consistent and literarily ambitious. The fact that the material is constantly pressured by gaming needs to have a popular slant and multiple stylistic possibilities only adds to the cleverness and kaleidoscopic tapestry. Arthurian fantasy is usually written in a very dramatically focused way, putting important characters in the forefront, and usually over-emphasizing Mallory and a few other sources; not so in this masterpiece.
Other games that feature something resembling this level of quality in at least some of their material include the likes of JAGS Wonderland, Cyberpunk 2020, 2300 AD, Ars Magica, Polaris (hey, they don't all need to be long works)... there's probably quite a few games that I'm not thinking of right now. Obviously a remarkably high level of literary quality isn't the most common thing (wouldn't be remarkable if it was), but I find it highly likely that there are games that I'm not thinking of, or even ones that I haven't ever read.
So, can you point me towards any new candidates for my discerning list of remarkable literature in rpgs?