YAML 1 is an example of a hierarchical data storage format which is much more readable than XML. The problem with YAML is that it was designed as a “data serialization language” and thus to map the data constructs usually found in programming languages. That makes it too complex for the simple task of storing plain lists of items.
I dont see how this is true. Provided sample with books is almost identical in yaml.
The main benefit over yaml looks like more control of individial fields but again, yaml based db app could do that too.