Ren'Py is a free, 2D, and cross-platform engine that helps you make story-based games including visual novels and simulation games. It uses a scripting language based on Python.
This engine is actually very easy to use and as long as you have the skill to make the art, music, and story (Or at least have a team of people willing to help), you can make a Visual Novel VERY easily and very nicely with this engine.
It's free, and not too hard to understand. It even has it's own tutorial game that goes rather in-depth with it's controls and scripting.
Frankly, if you're into Visual Novels and you want to make one of your own, this is an Engine I highly recommend. All you need is your own art, music, and story, and with help from the tutorial (or prior coding knowledge) you're pretty much set.
Very few things I found a little annoying but other than those this engine is pretty much wonderful in most ways.
Give it a download and a try if you want to make a VN.
It's worth the few seconds it takes to download.