You can sign up for Twitch Prime at that link, if you haven’t already. If you’re an existing Amazon Prime member, you can just link your Twitch account to get at the free games, and you can claim the titles with a trial, too. The games will download through the Twitch client, but they’re typically DRM-free installs and can be launched without the program running.
The headline title this month is certainly Observer, the Rutger Hauer-led cyberpunk horror title from Layers of Fear dev Bloober Team. But don’t overlook the others, either. Forsaken Remastered is an updated rival of games like Descent, Steel Rats is an attitude-heavy tale of bikers fighting alien robots, Project Warlock as a Doom-inspired tribute to classic shooters, and The Flame in the Flood is a lovely roguelike set in the aftermath of a ruined America.