Recently I wanted to read something about graph databases and in the Humble Book Bundle, I found Graph Databases by Jim Webber, Ian Robinson and Emil Eifrem. The book is mostly focused on neo4j but has a bit of information about other databases. It has examples of graph data models and real world use cases, also the book contains an information about theoretical parts and neo4j internals. And there’s a lot about Cypher language.
Although in some chapters the book can be described by anything’s a graph if you’re brave enough.