That doesn't seem very fair. They link a docs folder and an overview document, neither of which require that the user read code to get a good idea of the librar

That doesn't seem very fair. They link a docs folder and an overview document, neither of which require that the user read code to get a good idea of the library's contents. That said, the code is also reasonably well commented as well, for example: https://github.com/facebook/folly/blob/master/folly/Singleton.h https://github.com/facebook/folly/blob/master/folly/Singleto.... So "read the code" is not terrible advice in this case either.