Since the release we've had a huge amount of people asking us about the campaign mode, why it wasn't included in the steam version, and why the documents for it have still been available. Here's a post with a full explanation and details of what's happening with the apocalypse's campaign mode.
As our longer lasting community members know, we had a large campaign mode in all the updates available to testers before 0.1.1.3 (the release version). Basically, all the characters models, textures, the motion capture data, and the voices for all of the characters were finished. We'd also finished the prologue content, and the chapter 1 content, the vehicles, the first and second map, two large interior maps, and much more. You can see this from the footage on the trailers, and a few screenshots from our website.
However, all the updates after 0.1.1.3 have been completely different in regards to the campaign, which couldn't be considered a campaign due the lack of everything mentioned above, and more. This is why some community members have posted on the forums with negative comments aimed towards us, only to change the posts themselves and apologize to us.
This is all due to a few weeks prior to the release, our official apocalypse writer had a few unfortunate problems last minute, which led to us losing all contact. I must mention, that he wasn't to blame for this, I can't disclose more though due to privacy reasons. However, because we lost contact for this long, the developer couldn't finish the work, and we had to cut everything made related to the campaign and replace it with a tutorial style experience instead. We couldn't include a feature half-finished, as this was an issue with valve and the release guidelines, which is why we didn't leave the content as-is.
We now know what happened from his end because he reached out to us recently and told us what had happened, and that he will now resume his work. This means that we'll slowly begin re-adding all the content which was cut. We've always kept the documents available to the public since he created them months ago, for those that were unaware, you can access them by opening the correct .ap files included in the downloaded game folder with microsoft word.
So as an overview, the campaign mode that was available prior to the 0.1.1.3 is now slowly being re-added, and kept updated by the official apocalypse writer!
If there's any questions, let us know!