There are some libraries at Json.org . I compare all of them below

I think the best solution is cajun. Here is sample of code, that shows how does it work. We have such json request in file example.in

{
    "description": "subscribe to channel",
    "type": "object",
    "properties": {
        "user": {"type":"string"},
        "channel":{"type":"string"}
    }
}

Below you can see programm that prints its data to std::cout.

#include "elements.h"
#include "quick.h"
#include "writer.h"
#include "reader.h"
#include "cast.h"
#include "exception.h"
#include <iostream>
#include <fstream>
 
using namespace json;
 
int main(int argc,char** argv){
	std::ifstream in("example.in");
	Element elemRoot;//Root element of request
	Reader::Read(elemRoot,in); // Reading document into elemRoot
	QuickInterpreter interpeter(elemRoot);// This class allows us to get access to elemnts of json request like in std::map
	const String& description=interpeter["description"];
	const String& type=interpeter["type"];
	const String& type1=interpeter["properties"]["user"]["type"];
	const String& type2=interpeter["properties"]["channel"]["type"];
	std::cout << "description:  " << std::string(description) << std::endl;
	std::cout << "type:  " << std::string(type) << std::endl;
        std::cout << "properties/user/type:  " << std::string(type1) << std::endl;
        std::cout << "properties/channel/type:  " <<  std::string(type2) << std::endl;
//Creating json request
        Element newRoot;
        QuickBuilder builder(newRoot);
        builder["description"]=String("subscribe to channel");
        builder["type"]=String("object");
        builder["properties"]["user"]["type"]=String("string");
        builder["properties"]["channel"]["type"]=String("string");
        std::cout << "Example of creating json:" << std::endl;
        Writer::Write(newRoot,std::cout);
        return 0;
}