Last I read Swamp Thing, it was with the JLD. I know he played a role in Endless Winter before the new mini series. But is there anything else I need to read?
The current book The Swamp Thing is completely independent of the previous stuff. However, if you wanted to get to know more about Swamp Thing I suggest the first two story arcs from Alan Moore. I would say to also read House of Secrets 92, Swamp Thing’s first appearance, but that is not needed as it is reprinted in one of the Alan Moore books.
If you wanted to just get down with Endless Winter, feel free to. It is a great read and Swamp Thing is excellent in that story!