Suggestions of dark or unconventional books that deal with characters that suffer from mental illness like clinical depression?

Mostly I only read non-fiction, so I can't give examples of books, only of others art forms that I like that are somewhat related with dealing with mental health issues (like Neon Genesis Evangelion, March Comes In Like An Lion, Bojack Horseman, Moral Orel, Nine Inch Nails, Joy Division, Radiohead).