If you are debating which library to use, don't make our mistake and try something else, as Mongoose Web Server Library does exactly what it needs to do. We started with a different C++ library that seemed like it would be easier to use, but it was riddled with bugs that made it unusable for our purposes. All the issues we had with the other library were solved with Mongoose.
Mongoose was very straightforward to implement and we didn't have any issues integrating. The single source file design made it extremely easy to work with and made a very low impact on our build process. This was also part of why we chose it.

We looked through many different libraries and solutions, but with the Mongoose Web Server Library, just within a couple of hours, we built a proof of concept.
With the help of examples, it was pretty straightforward to build the server. The Mongoose Library manages everything related to the Network stack, from IP up to HTTP - everything just works. We faced no problems with the Mongoose Web Server.
We now have a stable solution for customers, everything based around a simple RESTful API built with the Mongoose Library.