The Game Ready tag means that the new drivers include all optimizations as well as SLI profiles and Geforce Expreience settings for the Killing Floor 2 game. According to Nvidia, the Killing Floor 2, which is a first-person shooter, uses Nviida PhysX Flex effects for blood, bile and other gore effects in the game.
According to the release notes provided by Nvidia, the new Geforce 355.98 WHQL drivers do bring some minor improvements and bug fixes as well as updated features and functionality for the GameWorks VR SDK.
As it was the case with earlier Nvidia driver releases, the Geforce 355.98 WHQL Game Ready drivers are also available for Windows 10, Windows 8/8.1, Windows 7 and Windows Vista in both 32-bit and 64-bit versions.
As always, you can download the new Geforce 355.98 WHQL Game Ready drivers via Geforce Experience software or at Nvidia's drivers page.