You need to consider the entire number between each dot in the versioning system I use. You played version 0.8.1, and the important part here is 8, which is way, way less than the current 41. The game was still in its infancy back then.
There is nothing to worry about with the content changes, but you should get the SubscribeStar subscriber version. The game has been enormously expanded since last you played it and is basically feature complete outside of NG+. The plan is for only one more "incomplete" version (0.42, again focusing on NG+) and then we'll jump straight to 1.00 in one go. That final update will contain a lot of polish for the entire experience, but apart from that, what's here right now is pretty much a finished, lengthy game.