The mod specifically edits the 'light templates' of these dungeons.

Things to keep in mind:
Undead will still be able to see you.
Falmer will still be able to detect you.
Dwemer machines will still be able to detect you.
Light will likely attract unwanted attention in dark dungeons.
Carry torches or keep your light spells handy, it is dark.

This addon works very well with Sounds of Skyrim. Also check out the 'Lightless Abandon Dungeons' Mod for an even Darker experience. Also See 'Rings of Light Enchantment' mod to light up those dark dungeons. Ill be working on craftable torches and such and possible lanterns.

Known Issues:
There was some popping issues before, but all should be fixed with this release. I will read my comments and continue to work on it ;)