Well, 'voices in my head' often implies some sort of internal mental experience. A 'dark story' related to it might be about a person who is haunted by these voices. Maybe they are voices from past traumas or repressed emotions that lead the character into a downward spiral of a dark and often tragic narrative. For example, the voices could be telling the person to isolate themselves from others, and as they follow these voices, they end up in a very lonely and desolate situation which forms the core of the dark story.
Here's an example. A soldier returns from war and has voices in his head. These voices are of the people he couldn't save. They keep telling him he's a failure. The dark story unfolds as he tries to drown out these voices with alcohol and drugs, but instead, he ends up losing his family and job, and sinking deeper into a dark hole of despair.
In general, the Evangelion mangas are considered good. They expand on the anime's universe, providing more depth and character development. However, it depends on personal preferences as some might find the style or pacing not to their liking.
Perhaps. The Evangelion fandom is known for its active participation in creating and consuming fan works. 'evangelion the one i love is fanfiction' could be popular if it manages to resonate with the fans' emotions and expectations. For example, if it delves deep into the complex psychological aspects of the characters, similar to the original series, it might gain a following. Also, if it provides a fresh perspective on the love stories within the Evangelion universe, it could attract a lot of readers.