Bethesda have released a playable demo for The Evil Within on Steam. The demo will allow you to play through the first thee chapters of the game, and transfer your progress to the full game if you purchase it at a later date.
The Evil Within’s initial release on PC was somewhat shoddy, but Bethesda recently released a patch that addressed a number of issues the PC version had. The update now lets you toggle between a 30fps or 60fps cap, disable letterbox-style black bars, and makes other adjustments as well.
You can grab a demo for The Evil Within on its Steam page.