Is the first post updated?

The list of missing manuals is outdated. For instance, it mentions Battle Realms and Dungeon Keeper manuals that are present in GOG bonus packs.

Yes, it's up to date. You can read the main entry to see what exactly is missing:

Battle Realms
• Manual that is provided has extremely bad illustrations (particularly noticeable for the various charts). Charts can be found here. No good quality replacement available yet.
• Winter of the Wolf expansion manual that is provided has extremely bad illustrations (particularly noticeable for the various charts). Charts can be found here. No good quality replacement available yet.

Dungeon Keeper
• Missing manual of Gold edition. Replacement available here.
• Missing reference card. Polish version available here (thanks to Paradoks). No English replacement available yet.

Good news, looks like replacementdocs is back up and running (since end of July, but I just noticed it...)

Also, with GOG no longer supporting GOGmixes, looks like Treasure's invaluable GOGmix is permanently gone. I'm leaving the link in tribute, even though it no longer works, since her work helped me tremendously.

Just want to say thanks again for all your work with this thread, it's much appreciated!

2 months late alright, but since there hasn't been any answers yet, I will provide some.

A working link for Powerslide's PDF manual can be found below:
https://drive.google.com/open?id=0BwpXI6_1f1OQMUxSRFlNZnZpUGM

Stuff like manuals, reference cards and maps should be OK. Anything else like artbooks or soundtracks should be avoided. As for Shovel Knight, you might want to wait until King of Cards and Showdown are released.

EDIT: Wow, just wow. Two months late and still I get ninjad.

Sorry, just saw this.

Sadly, no. Maybe someone else does. I'll remove it from the list and add it to wanted.
Found scanned manual here, but it's offline too.
https://www.gog.com/forum/powerslide/power_slide_manual/page1

(EDIT: or of course you can just use Grargar's link above.)

Show me what you have. If it's a website/wiki page, then the list doesn't include them. However there was an actual physical manual and a digital one, so if the html file is the same as the physical one, I'll include it.

If a regular physical version has them, I'll include them.

(Re getting in trouble: I sent a support ticket about this and PMed a blue. Both said it's OK to go ahead and they'll let me know if there are any issues.
So if GOG or the publisher asks for anything to be removed, I'll do it.)

Ah, thanks. In this case no, I won't include it.

The reason Shovel Knight is on the list is because physical versions did come with a more detailed manual (around 40 pages). It had pages dedicated to enemies for example. From what I read it was included in digital to kickstarter backers, but since a regular physical version included them too, I think they should be on the list.
Here are some images of the physical manual (not necessarily English or PC):
http://thevitalounge.net/forum/threads/the-shovel-knight-manual-for-vita.4214/
http://globedia.com/fisico-vs-digital
https://www.pinterest.com/pin/460282024396136621

Thanks. Added.

The just-released Amnesia: Memories is missing its manual. It can be found here:
http://www.ideafintl.com/amnesia/manual/amnesia_m.pdf

Thanks. Added.

So running out of space.

No problem, I completely understand! Though I will leave the link up in the odd chance someone else wants it.

But yeah, damn, that is a really nice old-school manual! Has anyone tried contacting the devs to see if they'd release it here as a goodie or DLC? I don't understand why it's still kept exclusive when it's been out for so long already...
If no-one's received an official answer from the devs, I'll shoot them an email when I get a chance.

Here you go:
Scourge of Armagon
https://drive.google.com/open?id=1lL8YcPAHFEaQFZxQQwVWnDRNZN3mDSXX
Dissolution of Eternity
https://drive.google.com/open?id=1whdTeLkHaNdo1xJmgXkZaIL2v8hRVzwU

Please let me know what do you mean by low quality of Quake manual. It's the latest retail manual and it looks just fine for me (about 700 kb PDF file).

Thank you! Added.

Hmmm, I rechecked and we've had some discussion about it here.
https://www.gog.com/forum/general/list_of_gog_games_with_missing_manuals_and_where_to_find_them/post53
https://www.gog.com/forum/general/list_of_gog_games_with_missing_manuals_and_where_to_find_them/post59
"It has most of the illustrations, the only thing missing is mainly the front page and background image. Still, I'll keep this on the replacement missing page too, in case someone can provide a scanned version."

This is really one of the borderline cases on whether a game should be included here. I mean the one provided has everything you need info-wise, but it would be so nice to have one with the iconic background images and original fonts. Compare the French one:
https://drive.google.com/file/d/0BwpXI6_1f1OQbU50STZ0WGFzMHc/view