Is it just the soundtracks? its not very clear to me because other than the first couple lines it just has the default editions description

thanks for the help :)

It includes the full soundtrack (across 4 "albums", over 3 hours by now!) as well as the audiobook (7 1/2 hours). I can really recommend it if you like the game's universe and lore :)

The audiobook can be sampled over on gausswerk's soundcloud:
soundcloud.com/gausswerks/brigador-book-chapter-3-sample
soundcloud.com/gausswerks/brigador-book-chapter-4-sample

and the two albums, as well as the two EPs making up the soundtrack on Makeup and Vanity Set's bandcamp:
Brigador, Vol. I
Brigador, Vol. II
Brigador, Uplink EP
Brigador, Up-Armored EP

It should be noted that the soundtrack is only in MP3 format, unfortunately.

I guess, if the quality isn't mentioned on the page, it's just "standard".

Bummer, because even on Steam it's also available in FLAC, so why not on GOG, as well?

Bit late responding to this but we did in fact upload the FLACs earlier this year to the Deluxe edition. You can choose between the standard mp3s and lossless audio. Do bear in mind that lossless audio is extra chunky in case your internet access isn't all-you-can-eat (about 1.5gb in total for all four albums).