3 books with the covers making a triptych. they've gone for a slight Mork Borg feel, but much more restrained. The books are about the text, with black text on white with few drawings, for the most part. But a couple of pages are white text on black or white text on red and much heavier on artwork. It's still text-driven, so no funky layout, but those pages have more a a Borg feel. The colour-pallette is black, red and white, with a tiny bit of green on one page in one of the books. I'm not a fan of the typeface they picked, but it's fine - just wish it had been a big bigger. And the silver page gilding is very shiny - looks awesome The Player's Guide is very thin at 50 pages, so reminds me of a my-first-reader cardboard-cover book.
Outcast Silver Raiders rules are fairly standard 6-stat, 10 skills, 20D roll-over. There are 3 classes (warrior, rogue, sorcerer) with another 10 optional ones. Big difference being scarcity checks (read: usage die) for almost all equipment - everything will break down sooner than later - and looting equipment is severely discouraged, economically and utility-wise. Sorcery and ritual magic are very different. The first is costly and the second is dangerous. The optional divine magic is pretty typically Vancian, but limited to the optional priest and paladin classes, and all three are strongly discouraged for Outcast games.
I've got some quibbles with the economics. It's meant to force scarcity and adventuring to raid enough silver. I think it would be fine in play, but it reads as heavy handed and artificial.
Where Outcast really shines is the Mythic North setting. That is an amazing book. So much stuff packed in there. In absolute numbers, it's only 88 encounters and 28 places but each has multiple pages of information, quest hooks, relations to other entries, etc.
I should have realized it from the R. Scott Bakker mention, but it wasn't until this morning that it clicked that the hive creatures (forget the name) are the Incoroi from Bakker's The Second Apocalypse. Not quite as genocidal, but that's probably because of the barely mentioned lizard people in OSR.
It's explicitly a low magic, high religious-belief setting, with demons and political intrigue (the last two not necessarily related). There's nothing in the setting that forces the religion - it's the faith and everybody follows it - unless you pull in the optional paladin or priest. Sorcerers are definitely outcasts and fairly rare, but they exist. The Referee books explicitly warns that the ritual magic can make players uncomfortable so leave it out if it's best for your table. Because of that, the demons in the setting are meant to tie into the rituals, but it's implicit, not explicit.
The land is thinly disguised medieval Scotland with the southern invaders a thinly disguised England. Which makes it funny that the church is based in Rome. And it doesn't say the religion is Christianity, but it's pre-Reformation Christianity.