Europa Universalis IV, is now available via Steam for PC, Mac, and Linux, marking the fourth installment of the game that defined the Grand Strategy Genre. With this release, Paradox adds Workshop integration to allow for easy sharing of mods to change your experience in any number of ways.
Given the set of tags provided by the developer, it would appear that most anything can be modded in the game, from the AI, to graphics, gameplay, maps, religions, and all the way down to the loading screens. There are already a few mods available in the Workshop to get started with.
To get started with creating your own mods, Paradox has created this handy guide
with a general overview.
You can buy the game now
with Steamplay, allowing you to play on PC, Mac, or Linux.