If you happen to head over to https://www.nuget.org/packages and look at which package has been downloaded the most there is a clear winner: JSON.net. It is in everything, every where. JSON is so wildly ubiquitous that I play a little game with myself when I start a new project: how long can I go before I need to serialize or deserialize JSON and need to pull in JSON.net. I rarely last more than a couple of hours.
But it turns out that there is a lot more that JSON.net can do.