Love is likely a main theme. Often in novels, when there are words left unsaid, it has to do with unexpressed love. Another theme could be regret, as not saying things can lead to feelings of remorse later.
The theme could be about unspoken emotions. Often in novels where few words are left unsaid, there is a focus on the things that are not directly expressed but are felt deeply by the characters.
Perhaps there is a family - a father, mother and a child. The father, for example, has a lot on his mind but doesn't share it, and the mother and child are left to wonder. The main characters would then be those family members whose relationships are affected by the unsaid words.
One similar novel could be 'The Fault in Our Stars'. It also delves deep into emotions and relationships. Another one is 'Eleanor & Park' which has a great exploration of young love and unspoken feelings. And 'Looking for Alaska' is also a good choice as it has themes of self - discovery and things left unsaid among the characters.
The 'a truth best left unsaid fanfiction' can be quite thought - provoking. It delves deep into the emotions and relationships of the characters. Sometimes it might take a darker turn which adds more depth to the overall story. It also shows the creativity of the author in exploring different plotlines within the fanfiction world.
I'm not sure without reading the book, but often in novels like this there's a protagonist who is likely to be at the center of the unsaid things. Maybe it's a young adult trying to figure out family secrets.
One of the main themes could be family secrets. Novels often explore hidden family matters. Another might be self - discovery as characters deal with unspoken things in their lives.
Well, without more context about what 'better left unsaid fanfic' is about, it's difficult to give a definite recommendation. However, if it's related to a particular fandom, say, for example, a book or movie fandom, you can join the relevant fan communities on social media platforms. People there often share and discuss their favorite fanfics, and you may stumble upon this 'better left unsaid fanfic' through their conversations.
I'm not sure specifically which 'best left unsaid fanfic' you should read as it depends on the fandom you're interested in. However, you can start by looking on popular fanfic platforms like Archive of Our Own. Search for the relevant tags related to the 'best left unsaid' concept within your favorite fandoms.