What is nihilism about?

I'm planning to write a book about nihilism and I have to say I'm overwhelmed by the volume of the literature, references, names and movements that are under the same concept. I know for sure that nihilism is not a philosophical school or a movement since it doesn't really have a specific philosophy, theory or belief that everyone could agree on. It's not a philosophy it's more about the lack of philosophy, or rather about a general feeling that we are lacking a clear direction or a philosophy for our lives. There is a big confusion and unclear ideas about it since it's mostly associated with pessimism and depression. These are rather the consequences and not the core ideas. I would like to understand more about nihilism and I couldn't find a good and clear source to start with.<br><br>What is actually nihilism about?<br>Is there a specific philosophy that nihilists follow? <br>Is there a specific movement, political or religious views that nihilists believe in?<br>What are the core ideas that everyone who calls themselves a nihilist would agree on?<br><br>&#x200B;<br><br>P.S.- I don't really care about references. I don't want to read a whole book to understand just one concept.