This is the tool that created the Endgames Visual Novel featured on Megatokyo.com in 2015. It generates pure HTML+CSS "linear" visual novels, though in theory it can be adapted for branching storylines.
Examine the demo.webvn to understand the syntax of the input files, and create assets for your characters and background scenes. Edit scenes.css to add new scene descriptions, and edit vn.css to change the look and feel of the text boxes.
Running python2 genweb.py demo.webvn will create a series of files demo_0.htm (and so on) for each of the music segments in your source file. index.htm is configured to load the first frame of the demo script.