Update:

Due to the multitude of complaints from the fans, Resident Evil: Revelations 2 for PC will be getting localized co-op. This proves that Capcom has had the ability to add the feature the whole time. We do realize that a lot of PC titles usually get their split-screen features dropped compared to their console counterparts, but Steam's original description for the game mentioned that it had localized co-op, which upset a lot of people upon the release of the first episode. Capcom has announced it is releasing a beta version of Revelation 2's localized co-op, which you can sign up for on its main Steam page. A final version will be coming but Capcom would like the fans to test it first.

Here's what was said on Revelation 2's Steam page:

Hello RE fans,

Following Resident Evil Revelations 2 PC player feedback, we've got some new information to share. The development team has been exploring various options and we're in the process of creating a way for players to utilize a local co-op feature

Soon we plan to release a beta branch on Steam which will allow two players to play the Story and Raid modes locally via a split screen. We want to get this feature in the hands of our PC players as soon as possible, so this option may not be 100% polished when it is released. Feedback from those who try it out is welcomed. For anyone who isn't satisfied with this option, refunds are available through Steam.

Original Story:

Once again, fans are showing that nothing is impossible if they set their minds to it and have brought localized co-op to the PC version of Resident Evil: Revelations 2.

Many things have come from fan creations — Dota 2, League of Legends, DayZ, Fifty Shades of Grey — and now a fan is bringing us local co-op for Resident Evil: Revelations 2. Kotaku reports that Capcom recently decided to drop the bomb that its newly released survival horror game wasn't going to have local co-op on its PC version. Of course, since Capcom had originally promised that the game would have local co-op in its campaign mode, some people felt this just wasn't right. While most tucked their tails between their legs, others decided it was time to take action.

FluffyQuack is a well-known Resident Evil modder and has already debuted an early build of his co-op mode. He has managed to make local co-op happen in less than a week since the release of Revelations 2's first episode. The mod isn't completely finished yet, it's at least better than what Capcom is doing for it, who doesn't seem to have any plans to patch the game in the future to add the co-op that it misled fans into believing they would be receiving.

If you're an impatient lot, or just want to see what this co-op mod has to offer, you can download Fluffy Manager now and start messing around, but be warned — it is still under construction and therefore will still have some bugs.