How to write Beautiful Native Libraries?

I am c++ developer,I am planning to write a library/module in c++ which is used by some set of users/application on Cross platform.

I am learning library/module writing, According to my experience and some reference I have created some set of rules for myself :-

Tools Preference :-

• To create cross platform library Projects I will prefer to use CMake
• To do active development I have choose MSVC Compiler and Visual Studio Editor because It has powerful debugging feature.

Code Organization :-

Header Files =>Private(Folder)
             =>Public(Folder)
Source       =>Src(Folder)

Project Organization :-

 XXX_Library => Headers
                Src
 XXX_Test   => Headers
               Src
 Examples   => Src     

Coding Rules :-

• While exposing an Interface I mainly use C Language to avoid Cross
  Compatibility issues.
• Use Error Code instead of exception
• Always use Type-def if using any Third party library
• While writing an class I will try to Follow SOLID

Those who are experienced in library Writing please share your views that will be extremely useful for me.

such as,

• any obvious design pattern every Library/Module writer should follow?
• any Well written open source library to refer ?
• any Well written book every Library/Module should follow?