From Ren'Py Visual Novel Engine
The first tutorial you should read is the Quickstart manual, which teaches you how to make your first Ren'Py game.
The NVL-mode tutorial teaches you how to create games where pages of text fill the screen.
The web tutorial covers Ren'Py in greater detail.
You may like to view the simple introduction to the Ren'Py language:
The style customization tutorial focuses in on how one can use the style system and style inspector to change the look of the various styles in the game.