RapidJSON is my preferred library for dealing with JSON files. The archiver
works well for my needs to save and load 'project' files. The arhiver example
shows using overloads of
operator&, which is convenient for loading and
saving class members in to a JSON string.
I like to save files in JSON format because it is human readable. Your eyes will thank you when there are file problems and need to dig through and debug a file.